For most companies you register on line. Some may have you download, sign and mail or email back to them, a W-9 (certification of your SSN). Most have nothing for you to download when you register.
Once you are registered you can view their job board and request jobs. If you receive the job, some may have you take a certification test once you have read the instructions, but this is all on line. All shops have guidelines/instructions. Some shoppers choose to print these, some choose to download and save them to their computer, some with familiarity with the shop may just read them on line to note if there are any changes. You also need to look at the questionnaire you will fill out and again some choose to print, others just review. You perform the shop according to instructions, which usually include getting some form of 'proof of visit', which may be a receipt for a purchase or a business card or a photograph (your instructions will tell you what is needed). You will need to scan or photograph your receipt or business card to upload with your report. Your report is then reviewed by an editor and they will contact you if they have more questions or issues. Once your report is accepted you wait for payment. Some companies pay by check (fewer and fewer), most pay by sending money to your Paypal account, some pay by sending a direct deposit to your bank account.
All of which is to say that there are computer skills needed, but they are worth working your way through because you will be using the same ones over and over and over. There is very little that you actually need to download or print, though as mentioned above, some folks do print a lot when they are getting started.