Congratualtions, Sarah!
This is very exciting.
Are you on a fixed, flexible or responsive schedule?
If you are on a fixed schedule, I'd say the best thing to do is set up routines. Model them and have learners practice. This way, they know what to expect when they visit the library. Read a fun book if there's time.
If you have a flexible or responsive schedule, visit with teachers to find a time for library orientation. During orientation, show learners where resources are, how to use them, and how to check out books. Give them time to practice.
I know this is very basic, but setting routines helps learners feel comfortable because they know what to expect.
Is there an assistant in the library? If so, ask them about the routines that work in the library. Also ask them about areas that need improvement. Work together to make the first few weeks a smooth transition into the new school year.
Good luck! And enjoy. The best advice someone gave me during my first year was don't try to do too much. Instead, listen. Attend all meetings and think about how you can support the learning community with library resources.