How long should I charged new battery in MacBook pro?

Charge to 100% before disconnecting from a wall outlet.

Apple - Batteries - Notebooks

Charge to 100% when possible. But its not life or death. If you have to take it off early its not a big deal.

You can leave it plugged in all the time if you wish.

Once your Macbook is fully charged, it stops charging.

You can see this if you click on your apple logo, about this mac, more info, system report, power.

In any event, it is also a good idea to use your Macbook under it's own power to keep the battery in optimal condition.

As much as possible, try not to fully discharge your battery. It could do more harm than good to your Macbook.

Good luck and enjoy your macbook