If you need help with doing this physically, could you list your computer model? If you need help doing this on the computer so you can see yourself, can you elaborate which operating system you're using?
As far as software goes:
I will assume it is a fairly modern computer running Windows 10. You should be able to simply type "Camera" in start and it will bring up an app that can be used. Alternatively, this will likely bring up your manufacturer's Camera software as well.
If you wish to use this in a program such as skype, go into your options within the skype/other program, find the "Voice" or "video" categories, and the Camera, if it has been installed, should show as an option for the video input for Skype. Select this, and next...