do i charge my new phone when i take it out of the box or what?

Take it out of the box and charge it. OR wait till you want to charge it OR don't charge it. The choice is all years. There is no special rule of when to charge your iPhone. Charge it when you want to and as long as you want to. Your iPhone has built-in protection over charging. Enjoy your iPhone.

Axel F.

There is no need to charge your new phone till the battery gets low

Just don’t let the battery drain completely.

Either.

It makes no difference.