Both
batteries will come with some charge in them to start with, so you use your new toy straight away.
My advice would be to put the spare battery into your charger as soon as you get it. It shouldn't take more than a couple of hours to fully charge up, hopefully that will be a short enough time for the other battery to last so you can start to appreciate how its all going to work for you.
As soon as the spare battery is charged, that's when the light turnd green, change it and put the other battery on the charger. That way you will always have a fully charged battery ready to use.
Did you buy any spare atomizers and
batteries ? If you didn't you should do so as soon as possible. Atomizers do fail, if you've only got one of them, you will be with a unit to use until the replacement arrives.
I keep two spare atomizers and two spare batteries on hand for exactly that reason. Right now I'm waiting on 2 e-cigarillo atomizers. 1 penstyle atomizer & 1 penstyle battery to be replaced. If I didn't have spare parts here already, then I'd be without something to use.