In order to upload individual source files to Tapegerm you'll need to have a special Source Contributor profile added to your main account. Just ask via the contact link at the top of every tapegerm.com page.
You may upload sources at any time. You may choose to assign them to projects or not. All the sources you upload via your Source Contributor profile are available on your own Open Source Page, along with compositions which utilize any of your sources.. Here's David Fuglewicz's page
Assigning source files to a Tapegerm project is open to many methods.
You may assign sources to projects individually by including "project-37" somewhere in the credits or description (where 37 is the project number indicated on a project's page). You can do this at any time, even retroactively. You may also assign a source to multiple projects if you wish.
You may assign sources you have anywhere on the web to a Tapegerm project by creating a "blog" post. Here's what a blog post might look like. This is a screenshot of Dave's contribution to the Free Loop Pack 16:
As you can see, the source has been uploaded to archive.org. Here's what this looks like as it appears on the project page:
You could enter a longer description if warranted. Everything you enter in the "Entry Text" field will show. Feel free to play around with it. It's made to accommodate options we probably haven't anticipated.
You may also start your own Tapegerm project. The options there are just as open. Click on the Projects link in your Main profile control panel. Here is what the entry for the new Free Loop Project looks like:
This project had no source files to begin with since the project was about taking sources from other contributors. Another project might have sources uploaded into the project vault (zip, wav, mp3, etc. are allowed) while allowing or disallowing additional contributions. Or you could choose to feature sources you've uploaded elsewhere by linking to them in your Entry Text field. It's up to you.
Tapegerm Projects are made to accommodate a variety of methods, probably possibilities we haven't anticipated.