Stores have different team member entrances. If you aren't sure where to go then stay at the entrance doors. They have to open the doors for guests to come in to shop....and you can enter at that time. Don't worry about being there when the store opens.....they'll forgive you and show you what door to use for your next pre-opening report time.....the door that they show you is probably the same door to use after the store closes and the front doors are locked.
Good luck! Don't be overwhelmed by all the things that you have to learn....we've all been there.....and we've made it through.
My only advice to you......don't be afraid to ask questions....even if you have to ask the same question 101 times to the same person. In general, it is much easier to prevent a problem than it is to fix it. Don't worry.....they can fix everything!