With MultiBit Classic, you can have as many wallets as you like. They are usually given the file extension ".wallet".
When you open MultiBit Classic, the wallets that were open in the previous use of MultiBit Classic are reopened. If this is the first time you have opened MultiBit Classic a new, empty wallet file called "multibit.wallet" is created in your user data directory.
Your wallets appear in the side panel labelled "Wallets". Click on one of the wallets to make it the active wallet. The balance for the active wallet is shown in the top left of the MultiBit Classic screen. The wallet description and file location are shown in the title of the MultiBit Classic window.
To create a new wallet, click on the "New Wallet" button or choose the menu option "File | New Wallet". This opens a dialog window where you choose the location and file name of the new wallet. Click "Ok" and a new wallet is created with the default description "Your wallet description".
To rename the wallet, simply click on the descriptive text and type a new description. This change will be saved in the "multibit.info" file in the application directory when either the wallet is closed, or MultiBit Classic is shut down. This does not change the file name of the wallet.
To open another wallet, choose the "File | Open Wallet" menu option. This opens a file chooser dialog where you can choose the wallet to open. When the wallet is opened MultiBit Classic automatically synchronises it to get the latest transactions.
Note that MultiBit Classic cannot open the wallet files from the Satoshi bitcoin client (wallet.dat files).
To close a wallet, choose the "File | Close Wallet" option. This saves and closes the wallet and it is no longer shown in MultiBit. It is still stored on your disk - it is not deleted.