The folks at Wikispaces have created a video with screenshots to help clarify how to Upload Files. Their video can be found here:
http://www.wikispaces.com/content/wiki-tour/files

It's really easy -- All pages are basically .doc files with embedded file links.

1) Go to the page for which you have something to offer. Log in and click Edit This Page.

2) Enter the name of the Lab in bold and a short description. Enter your name in italics.

3) To upload a file, click on the TREE icon above and BROWSE to the file on your local disk. Click UPLOAD. Your file is now uploaded into the file list, but it's not available for anyone to use -- yet.

4) On the page you want to edit, position your cursor to the location you want the link to be inserted. Now double-click the icon of the file you want to upload.

5) Save the page.

Space for testing file uploads:

Lab name - short description - my name