RaceDay Scoring allows you to import participants from a CSV file. You can do so by navigating to the Participants Tab:

Next, click the Import button in the toolbar:

Next, click the Choose File button:

Next - map the fields coming in from the Spreadsheet to the fields in RaceDay Scoring, and select Set Field Mappings at the bottom of the page:

If you have Event Names in your Spreadsheet that do not match the Event Names in RaceDay Scoring, you can map them on the next screen. In my Spreadsheet I had "A" as an Event, which actually should be "5k"

After mapping the fields and clicking Continue the import will be complete:

You can click the Participants tab to view the imported participants: