Dumb question concerning on board water tank

Find the tank fill and use a hose and funnel for the bleach as others suggested. Put in about 20 gallons of water and go for a drive so the water\bleach sloshes all around the tank. Drain and fill your tank normally. If you can still smell the bleach do another fill and drain. While I won't drink straight water from my tank, I will use it to make coffee. Can't say I've ever been sick from the tank's water.