In Fallout New Vegas I have a "varmint rifle" and I purchased a "varmint rifle night scope" from Chet in Goodsprings.
How can I put the scope on the rifle?
My first thought was that I should simply go into the Pip Boy and equip the scope, but the option to do that is greyed out.
I tried doing that with the rifle equipped and without.
I also tried activating a workbench, but there was no recipe to modify the rifle.
My character has a "repair" skill of a little over 50.
Best Answer
You have to select the weapon, and then hit the weapon mod key/button:
Then you'll switch to a list of the available compatible weapon mods for that weapon, and you can pick one to attach.
(As a side note, if you want a better Varmint Rifle, you may want to go looking for Ratslayer - it is a stronger variant that has all the mods already equipped, but with better stats. Getting to it can be tricky, though.)