Incorporating pumping into the routine

Hi! Im a first time mom! My baby will be 3 weeks in 2 days and we exclusively breastfeed. I will like to start incorporating pumping to build a stash for when i go back to work, im not necessarily going to use for bottle feeding at the moment as i am on maternity leave for another two months. How often should i pump and when (before or after feeding) (immediately after feeding or an hour afterwards). I have no one to really ask about these things!

Thank you in advance!!