@helpme122
As far as the tank not working, check it on another device if possible, check the charge of your battery, and if everything is good there then possibly look at prying up the center pin a bit as it must not be making connection (possibly overtightened before).
@MsShona
Firstly you have to check that your device is capable of firing sub-ohm clearomizers. All devices will come with the resistance range which they can fire between. Next is the batteries, you need a high amperage battery. The most common and well regarded ones are Samsung 25r and Sony VTC4, ensure you get genuine batteries though.