Help resetting Dell running Windows 8.1 English 64 bit

The computer is packed with viruses and it's nearly unusable, and I think a factory reset is my only option. When I click Get started on the option in the Recovery tab of the Update and Recovery section in the PC Settings, It brings up a screen that says "Please wait" and in smaller text below that a spinning circle of dots and the word "preparing." After about 3-4 minutes on average, that text is replaced with "Insert media" in large text, and then in smaller text "Some files are missing. Your Windows installation or recovery media will provide these files." How do I get past this screen to initiate the factory reset? I'm not very good with computers, and I'd be very grateful if anyone could help me with this predicament I'm in.

I found this on the Dell site. This is for Win 8 machines.
Here is the procedure.
Dell Backup and Recovery 1.8: Recovery | Dell US

Thank you, fireberd for the reply, but in step 5 for the steps in the site you linked, it instructs to click the "Dell backup and recovery" option in the "Troublseshoot" section. This option does not appear for me. Only the other three do.

As yours is missing (or corrupted) you will then need a Win 8.1 install disc to reinstall.

Your computer should have come with Dell software to make a factory recovery USB flash drive. You probably need one that is 32GB in size. It is the first thing I do when I buy a new computer. After the flash drive is made, label it, put it in a safe place, and don't use it for anything else. I always buy a good quality, new, flash drive, but a used one will also work.
If your hard drive ever goes bad, or in situations like yours, you can use the flash drive to restore the operating system.

You will not be able to restore the operating system if the new hard drive is smaller than the original. I found that out the hard way.

Here is a guide to make the flash drive.

Dell Backup and Recovery 1.8: Factory Recovery Media | Dell US