If your browsing the apps on your PC: Download "Barcode Scanner" from the Market on your phone, then use that app to scan the QR codes on Phandroid. After scanning, Barcode Scanner will then give the option to "open link in browser," select that and it will direct you to the Market to download whatever apps code you just scanned.
If your browsing on your phone: Just click the QR code as if it was a link and it should direct you to the app on the Market.