I want to transfer the bitcoins I have from one address to another one, however I can't acces the account but I only know the address. I made this once but I forgot how, it was some sort of program which I selected from what address I wanted to transfer the bitcoins and it was done easily. I tried some programs now and I can't do that anymore. It was something like "add bitcoins" and I just typed the address from which I had bitcoins on and the bitcoins transfered automatically.
It sounds like you used a Bitcoin wallet to move money before. You need to know more about the account than just the address, in order to move the money out of that address. With the address, you can look at how much money the address has, and add more money to it, but you can't take money out.
If you had the private key, which should be kept by the Bitcoin wallet, or written down somewhere, you could spend this. A private key looks like
Unfortunately, I don't know which program you used, so I can't tell you anything more specific. I can point you to this list of Bitcoin wallets. Maybe you used one from there.