I can see you payed £699 so I assume you're in England too! For what it's worth I would take it back and ask them to check it / set it up to your preferences.
If you want to do it yourself... action and relief are (obviously) linked so I'd set the relief first and then set the action. (Easier said than done if you don't have any tools to measure what you're doing, although you can use a capo and cheap automotive feeler guage set for relief) .
Truss rod spec is 0.010 of an inch measured at the 8th fret - see link below for the method. I set my two PRS at about half of that using a notched straight edge and a set of luthier feeler guages I bought from Crimson Guitars in Dorset - they're both really nice so if you're happy spending the money they're worth it. I use a StewMac steel ruler imported from the States for measuring action - I love the StewMac ruler but I'm sure Crimson will have something similar.
Truss rod spec from the PRS website:
https://www.prsguitars.com/index.php/support/article/prs_double_acting_truss_rod_adjustment
Spec for action is 5/64th on the low E measured at the 12th fret and 4/64th on the high E again at the 12th fret. What suits will obviously depend on the guitar and your preferences (one of mine is down at around 3/64th both sides, the other is closer to the recommeded specs as it won't set as low as the other).
Setting up a stoptail:
https://www.prsguitars.com/index.php/support/article/prs_stoptail
I'd also want to be sure the nut slot was not cut too low. A quick test suggested by Dan Erlwine is to press a sting down at the third fret and tap on the string at the first fret - there needs to be at least a bit of clearance (I think Dan aims for 0.008 inch low E and half that on the high E). He also says using a capo frees up both hands doing this.
Dan's book '
Make your Eelectric Guitar Play Great' is great too if you like tinkering.
Good luck!
