I'm not clear on why you'd want to re-open your produced video clips in PD, but if it's to start a new project, you'd simply import the clip(s) from their current location and edit as usual.
If instead you're asking about reopening an
existing project after you've moved the source files, you'll need to use the Browse tool that will appear when you reopen the project in PD and it can't find the clips in their original location. Once you've located them, be sure to save the project (or use Save As) so the clips' locations will be retained.
Finally, if you're asking how to always be able to open up projects without having to track down where the original clips have been moved (or if they've actually been deleted), you'd want to first use Pack Project Materials from PD's File menu and specify a folder where copies of all project materials will be stored.