Joining Plywood

I have 2 sheets of plywood meeting on a 90 degree angle, how can i finish it off so i don't see the end of one sheet if you know what I mean?

It depends on your skill with a circular saw, or with a table saw.

You can do an outside 45 deg miter cut on each sheet. you will have to be bloody precise, or it'll look like crap, OTOH if you get it right, it'll look darn good. That's why it depends on your skill level.

OTOH, you could join the two w/ a piece of 3/4 round (assuming the ply is 3/4", or even a square dowel of the same size as the ply. Obviously this isn't an option if you don't have internal support. OTOH, it's simple to get right, and pretty hard to screw up.