You can import submissions into a new form if you have a spreadsheet filled with the submission information.
Go to Events > Capture, then click on the dropdown on the top of the screen, and click on 'Import Event Leads' as shown:
Then choose the intended event and click Continue.
Then you will be prompted to upload a spreadsheet.
Map the fields to their corresponding Captello fields and then click 'Next'.
Click on the 'Next' button and then click 'Run'.