multibit - my wallet is not reopening
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.