Soffit vent repair

My soffit has a 2 inch wide vent and there is a portion of it that was
damaged (about 6 inches in length). I can cut a piece to replace it,
but I cannot figure out how to attach it from the inside. There is no

Assuming this is continuous screened vent, cut a piece that's too long
so it overlaps the good part of the old screen, and select a pop rivet
that's a good fit for the holes in the screen. That will squeeze the
upper screen down against the new screen.

way to reach it from the attic, it's at the end of it and it's way too
tight. So I have to try to do it from below, seems I have to glue it
since there is no way to nail or screw it but even using glue is not
going to work if I cannot apply any pressure on the other side.

I hope I don't have to open a hole in the T&G T-111 wood soffit just
to attach the vent. There must be a better way?

Why do you need to apply pressure?

Run a string through the vent and tie a weight to it to hold the vent down
while the glue sets. You might need a couple of strings to insure that the
vent lays flat.