To tax your car you'll need to have your licence registration and 12-digit V5C number to hand. Both can be found in your order confirmation email.
You can tax your car by registering at the DVLA.
Click ‘Start now’ and then you’ll need to select the third option - ‘V5C/2 new keeper supplement (green slip), which is just a couple of clicks after you’ve entered your details.
If you’re subscribing to a car, your tax will be sorted for you so you don’t need to do anything.