Once you add someone to your Pal List you can send them IMs. You are also able to invite Pals in to start private groups called 'Super IM'.
If you want to start an IM with anyone on your Pal List, just left click on their name, and a chat window will appear.
You can also right click on anyone in your Pal List, and select 'open IM' from the menu.
When in a chat room just right click on any member in the participant list, and select 'send IM' from the menu that appears.
Once you have opened the IM panel just type your text into the text entry area on the bottom of the panel. Press the 'enter' key on your keyboard to send the text.
You can hop between instant messages and the rooms you are in by using the 'active rooms' and 'recent' groups on the top of your Pal List. Just click on any item to instantly jump into their respective panels.