From My Roster, click Roster Import. Choose your organization and follow the instructions on the page - there is a template for each supported format, including the USA Gymnastics member export.

MeetMaker matches each imported person against your existing roster so people already on it are updated rather than duplicated. Matching now uses the membership number first, so a nickname or a corrected date of birth no longer creates a second copy of the same athlete.

Check the level and gender on the imported rows before you register - those are what registration depends on.