Well, if you only want them temporarily, then rename them to replace an opt. Then just play normally.
Frex, rename missileboat.opt
into missileboat 1.opt
, and rename Bob.opt
. Then start a skirmish and select the missile boat. Be warned, however, that the weapons might not function right (or at all); your new opt wil have the same stats as the old one.
If you plan for these opts to be permanent (and if they have shp files), get MXvTed and edit the stats (and shiplist, and strings, and specdesc) themselves. Just be careful to (A) backup your exe, and (B) don't delete/replace anything important.
MXvTed does a better job, but requires more time (usual procedure for me is install, play XWA and check settings, exit XWA, tweak changes, check again, tweak, etc. repeated until I get the ship functioning right).
<small>That's when I find out that the beautiful opt that I've just installed doesn't have hardpoints set, and I have to ask for opting help that never arrives.</small>
"Don't f_ck with the Jedi Master, son." --Mark Hamill