It's a bit tricky to launch your canoe with all your stuff in it, but you'll get quick at it with a little experience. If you have a dock, it's easy! If you're canoeing in the sorts of places I like to go, you won't have a dock and you'll probably get your boots a little wet. Some people just take them off to avoid that.
Don't load up your canoe on land, that's just silly. You'll risk damaging the canoe, because it was designed with the support of the water under it in mind. When you have it on land, all the weight in it is being supported on a concentrated area on the canoe's body which can crack it. You'll have a rough time getting it in the water with it fully loaded, anyway!
What I do is place the length of the canoe along the shore (when I have the option) such that the entire canoe is in the water and floating. You're going to get your feet wet, so plan for that! I clumsily drop my backpack in the middle of the canoe, zippers-up so that I can still get at the pockets where my map, compass, and snacks are.
Then with the canoe loaded up, I grab both gunwales (the metal-rimmed edges of the canoe), get a foot as close to the exact middle of the canoe as possible, and hop in, giving a good kick against the land which sends the canoe off away from the shore. It's a balancing act.
If you find yourself making ridiculous jerking motions to get the canoe off land, you're doing it wrong and scratching your canoe. Don't be afraid to get your feet a little wet, it'll make things easier!