There is also the Hastings Marina. Just follow 2nd street East till it ends >here< . Last time I launched there it was $10 but in my opinion it is worth it because it is an excellent high water ramp and has 2 docks. The Prescott launch can be difficult in high water because the top part of the ramp has a low slope so you may have to get your feet wet.
If you are fishing pool 3 above Prescott you will need to follow the inland water rules and below Prescott you follow WI/MN boarder water rules. Main difference this time of year is 1 rod for inland and 2 rods on boarder waters.
There are many wing dams to explore down river from Prescott. With the high water I would look for slack areas along shorelines and around the islands.