Have been trying to do a little each day before the cold weather sets in. Got the 2x6 wall studs up. In a post frame building (aka pole barn) they serve as nailers for the wall sheathing (7/16" OSB in this case) and "bays" for the insulation batts. They do offer some structural support, but your load is primarily carried by the top girts which then transfers it to the columns, to the concrete pads/collars surrounding the columns (poles) and then on down to the center of the Earth.
Really... well, more or less.
I've also begun to set the 2x10x20 attic floor joists. I'm toenailing them to the top girts (inside and outside girts) and also putting one Simpson Strongtie clip at each end. The joists are 12" o.c. which meets code for 18' 9" clear span. I'll also add 2x10 solid blocking (some call it bridging) between the joists which should make the attic floor super-stiff and solid underfoot.