To send bitcoin to someone click on the 'Send' tab (you can also use the 'Trade | Send Bitcoin' menu option).
At this point if you click send MultiBit Classic will show a confirmation screen giving you the chance to back out. If you proceed then your transaction will be submitted to the Bitcoin network and should be considered irreversible from this point on.
The Bitcoin network requires you to specify the destination address. Any of the following will work:
Add in the amount of bitcoin you want to send in the "Amount" field. You can type an amount denominated in bitcoin (BTC) in the left entry field or the amount in your fiat currency in the right entry field. MultiBit Classic will perform a currency conversion using your choice of exchange.
You should add a label for your personal records in the "Label" field.
You always get a confirmation screen before your bitcoin are actually sent. Click on the "Send" button to see this screen. Then:
Check the details on this confirmation screen to make sure the address and amount are correct.
Press the "Send" button to actually send the bitcoin.
When the bitcoin are sent, you get a message at the bottom of the confirmation screen. Also, the number of peers (other computers on the Bitcoin network) that you are connected to that have seen the transaction is shown. If there was a problem in sending your bitcoin an error message will be shown instead.