I have a logo/graphic in .png format, and I'd like to composite video within that logo. I know it has to be some mask effect or something to do with alpha channels, but I'm more of a beginner editor and can't figure out how to do this. Any help would be greatly appreciated!
MC might not be the best way to try to do this, but the basic idea is there and do-able.
Is your PNG keyable? Can you put it on V2 with footage on V1, and see both items?
If so, click on the key settings and try inverting the key. See what that does for you.
From there, it depends what you want to do. If you want to key that comp over some other footage, then you will need to do some playing to get that clip with the footage in it...to then have its own key channel.
Again, this is do-able in MC, but i would much sooner jump to Fusion or AE to do these kind of graphic jobs.
In MC, you will want to learn about matte keys, and how to bring in external mattes. Maybe some mixdowns to create your intermediate renders. You will not be able to play with transfer modes, unless you have some plugin kits, but i'm assuming if you are a beginner, you are dealing with the basic Avid setup and not using plugins.