To initialize a (pre)registration, pass the URL to a Google Sheet holding the (pre)registration form specification (in {preregr} format), see the "Creating a form from a spreadsheet" vignette), the path to a file with a spreadsheet holding such a specification, or a loaded or imported {preregr} (pre)registration form.
Details
For an introduction to working with {preregr} (pre)registrations, see the "Specifying preregistration content" vignette.