When roleplaying you will have to have your character sheet at hand to look at the different bonuses and such that you will have. To make things easier all the players will have to get their character sheet in their signature.
The signature is a small message that will be automatically posted after each of your messages. To access it you need to go to your Profile, then select "Signature"
After this a message box will appear, in here you can simply copy and paste the link to your character sheet but if you want to make it more unique you can select the "Insert link" option, it is the one with the chain icon to the left of the youtube icon, this will let you do links who are embedded in a text. The text of your signature can be anything you want, from a simple description saying your name and faction to something more flavorful like one of your character's quotes.
It is obligatory to do.