Is it possible to control a PC via VNC or SSH with a Raspberry Pi? If so what are the methods should I do to achieve this?
Depending on the setup of the PC you want to control, there are several ways to archive this.
Since you wrote about VNC or SSH I assume the PC is running some sort of Linux/Unix?
A SSH-server can be installed on (mostly) any distribution out of the box, for VNC the available tools are depending on the distribution (if you're not willing to compile from source). Just check which tools are available for your PC's operating system (e.g. from the "Software Center" in Ubuntu or "YaST" on SLES).
If you're willing to share a few more details on your setup, I could propably give you some more directions ;)