What they want you to do is to upload a file from your computer. This file would be your resume and I would assume it will be a Word or Office document depending on the extension (last 3-4 letters after the period at the end of the file name). If you have this saved on your desktop, you should be able to access it through Windows Explorer or as it is known in Windows 8 - File Explorer
--- sheesh I think that is what it was called in Windows 2.8 IIRCC
What you need to do is open File Explorer, check your c drive and expand your Desktop. You should see your resume file name there. Then go back to your application form, hit the browse/find/upload file or whatever it is called and then follow through with that window and go to the file you identified in File Explorer. Click that file and poof, there you go. I hope I explained that clearly. Either way, click the link above that says File Explorer and it will take you to the Microsoft help page.