Pay and print... enter your card information and once it's finalized you will get an e mail that has either a link, or a .pdf file of you tickets. You just print 'em from you home computer and you are good.... you can also have the barcode sent to your smart phone and have it scanned that way.
I just tried ScoreBig and got some tickets for a pretty good price for the game on Friday, $51 each for tix ~20 rows behind the Phillies dugout. I got a note that the tix will be sent via FedEx, which seems strange, that's a huge extra cost for the seller vs. just emailing me the tickets.
After the purchase I realized that I should have stuck with a round number like $50 even. On Stubhub sellers try to undercut each other so you see a lot of tickets for $29, $39, $49... On eBay buyers try to outbid each other, so you see a lot of bids for $51.01 and such. With blind offers on ScoreBig, there is no reason for a seller to drop under a round number, and with no competing bids there was no reason for me to go over a round number. Oh well, an extra $4 won't kill me and I still got a nice price.