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

Basically, put bleach into the tank and fill it, then pump the water into all your water lines-you should smell the bleach as it comes out of the faucet-let it set for 12-24 hours. Drain the tank and then refill with clean water and pump it to all the faucets until you DO NOT smell any bleach in the line. Top off the tank and you should be good to go. The amount of bleach for that big a tank should be around 1 cup. Quarter cup per 15 gallons is the general rule.