Reset kerning to import new one?

Glyphs
#1

hi everyone, need to import kerning values from other .glyphs but the option is grayed out (file, import, metrics). Why is that? I have other kerning values that i want to overrite with new ones. I have to reset the old kerning? how do i do that?

thanks

#2
  1. Window > Kerning, select all, copy
  2. Switch to other font
  3. Window > Kerning, activate it by clicking into it, paste
#3

i love u, thanks