I may be able to walk you through the process individually if you'd like, but overall the process is to get your scanner/software set to scan at a reasonable quality so the image won't be too small (low quality) or large (over the maximum file size), scan your card(s), then use one of several options to crop the card(s) and make sure everything is nice and straight (usually small adjustments in rotation). Once you have your files saved you can go to each card's page and click where it tells you to to upload your files. They'll then go into the approval queue.
Other considerations: make sure to remove your cards from one-touches/toploaders/sleeves, and try to align them to the scanner's edges if you can to get them straight. Orient them properly (you may need to rotate them 90 degrees if they're horizontal or vertical). And don't use any kind of function that automatically crops your images for you because they'll inevitably cut off more of the image than they should.
I hope that helps!