You will need to lift the lid of the gas tank by unscrewing the bolts around the tank area. You will then need to lift the gas tank watching any wires and replace with new gas tank and release the lid and screw back on the bolts.
Generaly there is one screw underneath the gas tank cover.Open gas cover just like you would be filling it with gas and look down near the gas tankand the lid remove the screw and then push the tank covet forward and you should be able to see everything you need to do from there.Very simple
On cruiser style bikes you simply drain the gas, remove the fuel lines, and remove the tank. On full fairing style street bikes you need to go through extra steps like removing body panels and other components first.
Motorcycle gas tanks are expensive! You might have a salvage yard where you could pull and older tank for a reasonable price. If your tank is rusting on the inside, you can clean it and use a "gas tank coating" system. You can find these kits at the dealers.
