Never used FW tank, need to sanitize for use next week, how?

We have two filters, Wally world cartridge plus filter that came with the RV. We use City water which has clorine in it, I understand you have well water so that may be an issue with you? We wash, clean and cook with that water, not a problem! If a concern, bottled water for drinking and cooking is an option. Unless severly contanimated washing with the tank water should not be a problem.