I installed SuperCollider. However it didn't appear in my app menu. Also, I can't make up any good command which could start the interpreter.
How should I run it?
You don't say how you installed supercollider, so I guess you downloaded the source code from the main website? If so, then you don't get any menu entry but you do get the commands. Run the terminal command
However, my recommendation is not to install from source code but to use the SuperCollider PPA here (the webpage includes instructions). When you do that, it additionally gives you menu items for "SuperCollider Emacs" and "SuperCollider Vim" which make it a bit more obvious.