For nickname, that will be the name you are seen as in the chat room. It is recommended you use your stable_name so it's not taken already. If you wish to change your nick at any time in the chat, type this /nick new_name_here

If you wish to make it so no one else can use your nickname, type this : /ns register pwyouwant youremailaddy. You will be required to "identify" to your nick each time you join. It should bring a box up on join, but if you ever are asked to authenticate or identify, type this : /ns identify pwhere.