Pretty easy. Search BBSAK (Blackberry Swiss Army Knife), download and install (PC) only. Hook up phone. Run BBSAK. The rest is pretty intuitive. The program is made for us low end tech types. If you need more help PM me here at CB or check for threads around here.
If the app works on your new device the easy way is to return to the point of purchase, set your new account details, and download again.
An app like Aerize Card Loader will allow storing apps on an SD card.