To send bitcoin to someone select Send/Request and then select "Send".
The Bitcoin network requires you to specify the destination address. Any of the following will work:
When you press the Send button MultiBit shows you the progress of the send as follows:
Sometimes your transaction does not broadcast cleanly to the Bitcoin network. When this happens you are shown a messages like
"Your spendable balance is lower". If this happens and you are in a hurry you can close down MultiBit, check your network connection and restart MultiBit. It will then rebroadcast any transactions that have not confirmed. Otherwise, simply leave it running and wait for the next couple of blocks (say 30 minutes) for the transaction to get confirmed normally. Your balance will update automatically.
Some people have reported transactions taking quite a long time to confirm under these conditions - even up to 24 hours later.
A change to Bitcoin Core in version 0.12+ involves replace-by-fee transaction support. RBF is an optional extension to a standard Bitcoin transaction that permits the sender to perform a repeat broadcast of an earlier failed transaction with a higher fee attached. Typically this is to "free up" an earlier transaction that has been accepted into the network as valid but because the fee is too low is being ignored by miners. Repeating the transaction with a higher fee allows the sender to override the earlier transaction in the hope that the miners will add it to a block.
MultiBit does not currently support the creation of these types of transactions and relies instead on setting an appropriate fee to the transaction to ensure timely inclusion.