You've worked in completely the wrong order.
Firstly, the neck will shift a little if wherever you are has a different climate to wherever Warmoth is. Most necks only need 24 hours or so to acclimate, now and then you'll have one that will take a bit longer. Even if your climate isn't too different, necks can still shift a little during shipping. So never judge a neck on first appearances, unless it is very clearly actually warped.
Secondly, you don't touch the truss rod until you've got the guitar together and strung up. You can't tell exactly how much force in either direction will be needed to balance the string tension, so if you try to adjust it before the guitar is completed you'll just be guessing wildly.
Third, you don't mess with the truss rod to change your action. That's the job of the nut and bridge. You adjust the truss rod to maintain the correct amount of relief in the neck so the strings can pass cleanly over the frets. Necks have to have some relief, mostly dictated by the string gauge, another reason why you can't try to get these things in order until the guitar is finished. I think far too many people have completely unrealistic expectations about what a 'straight' neck means and what consistent or low action really is. There will always be a curve, action can never be the same at the lowest frets and the highest. If you set it up as such, every time you fret a note you will just get a muted clunk as the string rests on all the other frets.
If anything, in my experience Warmoth ships their necks with the truss rod a touch too tight. I certainly would not be tightening it further.
Loosen the truss rod a little. Go slowly; it takes some time for the neck to adjust and settle. Turn the truss rod about 1/8th of a turn at a time, give it 45-60 minutes, then turn a little more. Don't turn more than half a full turn in one day. It's different whe you have strings on and the guitar's been used for a while, but on a brand new neck with no strings, you want to be extra, extra careful. You can't damage the neck by adjusting too slowly but you can write it off by adjusting too fast.
Once you've got the neck roughly back to how it was when it was shipped, find somewhere it can be stored where it will not get colder, warmer or damper than any other part of the house, i.e. not above a boiler, in a basement, etc. Then you've just got to leave it there until the rest of your parts arrive and put it together in one go. It only really takes a single afternoon to put a parts guitar together and there's nothing you can do in advance which will make it go any faster or easier; it's already as fast and as simple as it's ever going to be.
