the guidebook says that "when you open MultiBit, the wallets that were open in the previous use of MultiBit are reopened", but I've stored some money in a wallet that I created in a USB key. Now I am opening again multibit and I can't see this wallet. The .wallet and .info files are in the flash and I know its address so the problem is, how to do in order to see the wallet in multibit again? there is not an explanation of it in this short guidebook. Thanks for your help.
You can use the "File | Open" menu option to open an existing wallet. A file chooser opens and you can navigate to where your wallet is stored to open it.
Note that in the older code (v0.4.23 and before) your wallet does not automatically resync when you open it. You have to do this manually with a 'Tools | Reset blockchain and transactions'.
The current version (v0.5.9 or later) automatically resyncs wallets when you open them.
I think if you want it to use the info you musttransfer the wallet files especially the Wallet.dat files to your appdata folder on the C drive as the default loading folder is the appdata folder, uhnless you tell it to open the file from the flash disk or right click on it in the flash drive and tell multibit to open it the multibit will always look in the c drive in your appdata folder for the files it uses.