how do i extrude an object circular?

 From:  Magma
6927.1 
it seemed to be a really basic thing to do and therefor easy. however i am fairly new to Moi 3d so i need some assistance.

I´ve tried searching for guides but there are none that explains how to do this.

(The object is a 2d illustrator file of a fish which i need to make into 3D

Thank you for your time :)