If you want an easy way to upload screenshots onto the Database without messing anything up, and you don't mind using an external program, please refer to this video made by coolXX on how to do it.
If you want the slow, tedious way, please keep reading.
Take the necessary screenshots you need. You were told in the respective team sector guides when you should have done that.
Upload the screenshots into a hosting site. What we recommend you is to use Imgur, but you can use any other alternative as long as the link doesn't expire
Upload them onto the DATABASE based on your sector:
(For Merchants and Radders) In your DATABASE sheet, on the SS column, press Ctrl+K and paste the link of your hosted image
(For Runners) In your DATABASE sheet, input any text on the RETURNED column, select it, and press Ctrl+K and paste the link of your hosted image.