Replacing lamp holder, the feed is 3 wire (black,white,bare copper) the new exterior lamp holder is 2 wire; what to do with bare copper wire?

Look at new lamp and see if u have a green screw. This is a ground screw. Attach a bare wire to screw and a bare wire to box. Wire nut these 2 wires to the bare wire from feed.

If no screw, attach bare wire to electric box.

Chuck