Easiest entry from the US side is thru Prairie Portage.  You will need an RABC as there is no Canadian Customs there. 

If you can't or don't want to get an RABC then you can enter either thru Saganaga or else thru Crane Lake.  If you enter thru Crane lake you will almost certainly want to use Anderson's (my recommendation) or Zups to tow you from Crane Lake to your entry point on the eastern end of Lac LaCroix

There are many excellent trip options from any of these starting points.  If you can advise more specifically as to the length of trip you'd like and how hard you'd like to work (plus what species of fish you prefer to catch) I'm sure that you will find plenty of route suggestions forthcoming.