The Customs Dock is just inside the entrance to the boat basin (the only one in PA Harbor). Just southeast of the customs dock is a long pier which is all guest moorage. The entire marina is run by the Port of Port Angeles. The Safeway that Livia mentions is really the closest proper supermarket in that area. I'm sure there's probably some local, niche-type market(s) closer, but you'll have to ask a local about that.
There is also the option of the public dock just east of the ferry dock - the observation tower on it is prominent. There are multiple slips on the south side of this and it is closer to town (and the Safeway) than the boat basin. I am not sure if there is a charge to use this.
As for anchoring, anywhere along the south shore would be my preference (inside the 5 fathom curve) between the public dock and Buoy 1. The afternoon sea breeze typically builds out of the west. The western end of the harbor has many underwater obstructions and is subject to tug and barge traffic going to the paper mill. Just be sure to anchor
clear of the ferry dock and port docks. PA is a fairly busy little harbor, mostly tankers anchoring for bunkers/stores or awaiting a berth. Beware that the ships have crew launches that operate out of the dock between the ferry and public docks. They can throw up quite a wake.
FWIW - Not many yachts anchor
in Port Angeles. It is not the most protected harbor and the wind
does blow there quite hard sometimes (even in August). For just a day or possible overnight, it's suitable but I wouldn't want to be there in a gale. Just keep an eye on the weather
and you shouldn't have any problems. The bottom (like most of this area) is a sitcky mud.
As for the actual checking in with customs there, I've never personally done it in PA. If they're anything like Roche Harbor, it should
be relatively pain free, but they do expect you to follow the rules to a T (ex, only the skipper
is to disembark the vessel until cleared). Of course, I'm not Canadian so, your mileage may vary.
Have a good trip!