I am new to QB Enterprise and this is the first month I will be closing out. What are the musts? Can I run a report showing profits based on sales rep?

Welcome to the QuickBooks Community, jodieg.

Closing your books is an important step to make sure that your data is organized and all transactions for that monthly period were accounted for. QuickBooks Desktop creates automatic adjustments in preparation of closing your books at the end of every fiscal year. 

You can take a look at this article for more details: Close your books in QuickBooks Desktop.

Meanwhile, you can follow these steps on how you can manually close the books to lock transactions for that period:

1. Go to Edit > Preferences > Accounting.
2. Select the Company Preferences tab.
3. Under Closing date, click the Set Date/Password button.
4. In the Set Closing Date and Password window, select the Closing Date.
5. Enter the Date Password, and confirm it.
6. Click OK once done. 

Here's a sample screenshot for a visual guide:

Keep me posted if you have any additional questions. Thanks.