You know, at 4500 ft I'd be surprised if you'd didn't find 45 pilots to be a good solution to the idle and popping issue right off the bat. It's hard to know about the mains if you're going for K&N pods but surely you'll need to be somewhere in the 160 range at that altitude.
Turn the mix screw to the left to open it...you might as well run it all the way in (not too tight or you'll deform the seat) so you can count turns on the way back out. The counting bit is only good for a reference, you really adjust the screws for the best idle (and also run at 2K in 2nd) so each carb can vary and might be set slightly differently. Greybeard and The_Dog33 have both described this at length so I won't repeat it here...you can do a quick search and the reading will likely do you good anyway.
Once you get it pretty good then you need to think about getting the pair balanced for optimal operation.
