starrting a campaign

Hey, I'm a little stuck on how to start a Call of Cthulhu campaign. It's gonna be a conclusion to a series of overarching one-shots that I made when I first started being a GM for Call of Cthulhu. I know the conflict, lore, factions, and main villain I want to put in. I just don't know how the players will fit into all this. Any tips?