Hi there, dolphinz - welcome to the forum. It's great to see you here.
If you have a picture on your PC you'd like to use as an avatar (it doesn't have to be a BB one if you don't want) then e-mail it to LEE or Mark and they'll check it out for size and then tell you how to put it in your profile. LEE has quite a lot of BB pictures, so you could also ask her to select one of a particular housemate for you to use as your avatar.
To start a new topic, click on the big 'New Topic' button at either the top or bottom right of the page. That'll open up a new window so you can insert a title and then post your message.
Good luck - hope you enjoy posting here!