Assessment
I think you are slightly misunderstanding some things, but basically you are already on the right path.
Wallet
I signed up for a bitcoin wallet (coinbase) where I am given an id.
Great.
When you want to manage your wallet (send and receive Bitcoin, create new wallets etc.) on your local machine, that’s a must. On a side-note: in case you need something easier (meaning: with a GUI), you should take a look at the multitude of desktop clients which bitcoin.org points to; for example: Bitcoin-QT.
Pool
I joined a pool (Slush's Pool) where I verified my email and added my private? id from my wallet. They registered a first worker for me:
login: myusername.worker1
password: something given
That’s perfect.
Miner
(my hardware doing maths), Xeon processor …
Well, you didn’t mention any mining software yet – and that’s where you took the wrong turn.
Filling the gap with Mining Software
Now that you know that your “Miner” needs “Mining software” to be able to actually mine things like Bitcoin, let’s take a look at what you need to start your own mining efforts…
Since you’ve mentioned you’re using the Ubuntu operating system, you could simply dive into the Ubuntu Software Center to download and download one of the ready-build miners:
cgminer
In case you prefer to create your own build from the sourcecode, check the cgminer GitHub repository.
The easier way is to install a ready-made build from the Software Center, or by entering the following commands in a terminal window:
apt-get update
sudo apt-get install cgminer
Or you simply install “cgminer” via the Ubuntu Software Center:

bfgminer
In case you prefer to create your own build from the sourcecode, check the bfgminer GitHub repository.
The easier way is to install a ready-made build by entering the following commands in a terminal window:
apt-get update
sudo apt-get install bfgminer
Or you simply install “bfgminer” via the Ubuntu Software Center:

You can also create your own build from the sourcecode in case you prefer that. To do so, check the bfgminer GitHub repository.
CPU Miners
Personally, I would not recommend using CPU-only miners because they tend to be slower compared to the above mining software. The reason is simple: CPU miners ignore the potential advantage your GPU (graphic card) might offer. Having said that…
In case you prefer to create your own build from the sourcecode, check the cpuminer GitHub repository.
The easier way is to install a ready-made build by entering the following commands in a terminal window:
apt-get update
sudo apt-get install cpuminer
Or you simply install “cpuminer” via the Ubuntu Software Center:

An aside: This mining software project provided the sourcecode-base on which other projects like bfgminer
and cgminer
were build.
Running the Mining Software
All of the mining software that has been mentioned above comes with dedicated documentation that explains how to compile the software from sourcecode, how to use the compiled software, etc.
But to get you going, I will provide simple examples for both cgminer
and bfgminer
. I guess you already know how to open a terminal window to start software from a commandline. For the commandline-parameter data, I’m assuming Slush's pool
as you indicated in your question, as well as using your example login myusername.worker1
and the example password mypassword
.
cgminer
cgminer -o stratum+tcp://stratum.theminingsite.com:3333 -u theusername -p thepassword
bfgminer
bfgminer -o stratum+tcp://stratum.theminingsite.com:3333 -u theusername -p thepassword
cpuminer
cpuminer -o stratum+tcp://stratum.theminingsite.com:3333 -u theusername -p thepassword
Since most command-line parameters will strongly depend on your hardware, you’ll have to read the docs to see if you can tune things towards higher speeds. In case of doubt, --help
offers an initial heads-up on potential tuning options of the individual mining software.
That's it… as soon as you’ve got your mining software installed, up and running, you’ll be mining Bitcoin (or alike crypto-currency).
Good Luck – you'll need it
Unless “the Bitcoin fairy” treats you gently, mining Bitcoin using average computer hardware will produce more costs than profits. In the unlikely case you make “profit”, don’t expect hundreds of Bitcoins… rather think in a realistic range of a few Satochi.
Generally, mining is an electricity-vampire. In other words: you can trust in the fact that mining will increase your energy bill. The chance to make profit will depend on a whole lot of luck, and the actual hashing speed you achieve with your mining rig.
If you really want to get your hands dirty and make profit from mining, you’ll have to consider investing in dedicated hardware (ASICs and/or FPGAs) to achieve higher hashing speeds – which can be rather inexpensive, depending on what hashing speeds you want/need/expect. One thing is for sure: the more hashing speed you trying to achieve, the more you'll find yourself buying more and/or better hardware – which will again will increase your energy bill proportionally. and only you can decide where you draw the fine line between “hobby” and “investment”.
In the end, the amount of cash you’ll have to pay for electricity will have the strongest negative impact on your mining efforts and your energy bill will ultimately dictate your break-even point.