First, you can pump and breastfeed. I'd recommend trying to breastfeed every two hours (or more if your baby wants to). Your baby will greatly help stimulate milk production and if your baby can latch breastfeeding (even if you are planning to exclusively pump) is a wonderful skill to learn. I've often found that a baby can clear a clogged duct much quicker and with less pain than a pump and all the different pumping mom trick outs there. About 15 minutes after you breastfeed (or when you find time in-between feedings). Add in a pumping session for 10 minutes or so, and use the hospital grade pump provided.
The second option is to start exclusively pumping right away. This method I recommend you pump every 2 hours for 20 minutes, then switch to every 3 hours at night once your milk comes in (every mom needs a little sleep!). At first you may not get anything out from an entire pumping session - DO NOT GET DISCOURAGED! It may talk a little for the colostrum to start flowing. I can remember when being in the hospital after giving birth to my first child pumping away and cheering the first time I got two drops into a bottle. Babies need very little in the beginning - just a little of that extra good healthy colostrum can get them a long way. If you're not getting colostrum or your LC is concerned about your baby's weight (all babies will lose weight after birth), it's okay to supplement with formula. Formula isn't poison and doesn't make you a bad mom, sometimes its exactly what your baby needs the first few days while you get your supply going.