Do you mean MHP2G? Or MHF2?
If you mean MHP2G, see 'Download' over at the menu screen? Well, press X on it and you will be directed to the Download menu, and you from there you can download things such as 'Piggie's Fashon', 'Extended Quests', 'Challenge Quests' and much more. Note that you need Internet Access on your PSP while doing this, you can simply go to your Library or any other location that offers free WiFi Access.