Where can i get minnows?

so basically i really like fishing for b but its hard cause i have no clue what to fish with to catch b, so what i do is catch a small bluegill and use it as bait and that works, i have caught two b and a rather large snapping turtle in a day, but i want to make it easier and just buy minnows and use them. also should i chum the water before i start fishing?