Interacting inside the RP
On emotes
You can write emotes. Typing /e changes your textbox into emote mode. The chat colour will change and everything you write will automatically begin with your character's name. Everyone will know that your character is acting instead of speaking. This can be used to describe what you are doing, such as /e runs her fingers through her hair or /e slices the n'wah's throat.
Please note that speech appended to emotes is often overlooked by other players.
On talk
You talk to other characters by using /s - the "say" chat. Occasionally you can also /y - yell, which will colour your text red and it can be read from much further away. Other characters in general do not approve of yelling.
Please note that roleplaying is something that does not work without interaction. When talking to others, please give them the opportunity to reply. Think of this in real life terms - nobody likes that person who talks peoples' ears off. Don't do this. Don't textwall.
On not-interaction
If a character stands around and doesn't say anything, most people will assume that their player is afk. If your character is around, but not interacting, you need to emote this, maybe by /e has no idea what to say or /e doesn't really care and watches the butterflies.