In the forums sometimes I see the user name and below it the role of that person i.e an engineer etc how to do it ant idea ??
If you refer to the line immediately under the user name, like in your case:sebastian
You cannot change the "Beginner", other than by posting (It's a sort of rough post counter that is changed at certain post counts and is used on most fora) and "engineer" isn't a possibility at that line (although some of us are engineers of different flavors).
There is a single line that you can change (at the bottom of the block under your name) and you find it in Profile -> Forum Profile and it's called "Personal Text" - You could write "engineer" there, if you are and if it's important to you to tell the world about it.
You can also make a signature (not for spam though) that goes at the bottom of your posts - please make it decent, as multi-color/-font/-size etc gives other nausea and headache