It's a multi-step process, research-wise.
You need to research Construction first, which will give you Troops to research next. The first level of Troops will give you the Small Troop plus the new Category of Troop Weapons. Research that Category for the Ground Cannon and Small Weapons (I think I have that name right - it's been a freakin' long day!) for micronized Versions of your other weapons.
Additional research in Armour and Shields will eventually yield components in those categories small enough for troops, just as other unit goodies are scattered about the various research projects.
When you've got the tech, go to the Design window, select Unit Designs, New, Troop, and continue just like you would for a ship!
BTW, those anti-proton beams which aren't such a good value in the full size Version are pretty darn nifty in the small size!