I'm trying to use Krita to start making an only comic but I can't seem to figure out how to make a comic frame mask. I heard you could use the Vector tool but I can't find the vector tool and none of the tutorials I find online really help me. An help would be most appreciated.

Take a look at the various comic templates, they use exactly that technique. As for the vector tools, check the manual: https://docs.krita.org/Vector_Layers . Oh, and you could either buy (https://krita.org/en/support-us/shop/) or check out on youtube the Comics with Krita tutorial series.