OpenGL not supported - metal card needed?

Hi - I’m reading all the posts on this topic and I’m thoroughly confused! I’m not a coder - just a parent trying to get this on the computer for her son:) How do I get this metal card in and where do I need to go and very specifically what do I need to do to get this working? I just upgraded my MAC and very frustrated after hours of updates that I can’t do anything aobut it.