....that way you'll get the leverage and you 'll know that the mounts will line up. If its too tough to move, use some an open ended spanner to get more leverage on the footpeg mount.
Or, alternatively........If that doesn't work, simply refit the footpeg, hold the bike upright from the front and whilst pushing it backwards, let go and make sure it falls on the right side, landing on the footpeg!!!
If you need further adjustment, just repeat the above process until you're satisfied that its straight!!!
If you overdo it, just push it forwards and drop it again!
I'll get my (carbon) coat!!