1. Go to Control > Query
2. Click on New and choose All Contacts Query
3. Under "Available Fields for Search", expand out Communities, expand out Forms, and click on Multiple Registration
4. In the window that pops open mark the checkbox next to your form name
5. Click OK
6. Expand Multiple Registration if it is not already
7. Click on Additional Contacts to highlight it
8. Click Add to move it over under Search Criteria
9. Click Next
10. This is where you can select all fields that will be displayed on the final results. Contacts > Profile > Profile Highlights should provide the majority of the fields you want.
11. When done selecting all your fields, click Next
12. Click Next again, unless you want to sort in a particular fashion

This will begin processing the results. You can click Save to save this query for future use, as it is dynamic and will update all new contacts for this registration form since the last time you ran it. You can also click to "Download Results (CSV)" which will export the results into an Excel file for you.