I was born in MN and spent a lot of summers around Grand Marais and up the Gunflint Trail, as well as around Ely in the Boundary Waters area.
The smart alek response is "there is NO fishing in Minnesota"
but honestly, there's more fishing lakes than you can imagine. The license plates reads "Land of 10,000 lakes" and I think they missed a bunch.
Depends on what kind of fishing you want to do (shore, canoe, boat, etc) and what kind of fish you want to pursue (walleye, northern pike, trout, panfish) but I would echo the post above to start with the DNR site, and maybe google fishing trips guides Minnesota for an overwhelming bunch of reading.