Video game piracy isn't usually prosecuted as viciously as music or film piracy, but that's no guarantee you won't get into trouble. Your risk is fairly low, but the only way to avoid legal trouble for sure is to buy PSP games on the up and up. When you pirate them instead, you're taking a chance. In the case of smaller releases, you're probably also hurting the bottom line of the game's developer and/or publisher. Think twice before pirating unusual or original games if you wish developers would release more of them. There are two basic ways to find PSP game files and download them to your computer.  Torrent game files. You can learn  how to torrent elsewhere on this site, but in brief, you'll need a program for running torrents, a torrent file of the game you want, and some time to let the program collect a copy of the game from other users. You shouldn't have to pay for the torrent or the program. Use torrent aggregators to search many libraries of torrent files at once. Select the files that have the most positive reviews attached to them, to ensure that you aren't actually downloading something you don't want.  Download games directly. There are a number of websites on the World Wide Web that offer PSP game downloads for free. Keep clicking through until you find a link to a download (typically offsite at a file hosting service such as uploaded.net or mega.co.nz), and click through to activate it. Generally speaking, the proper file extension for PSP game files is .iso. Make sure that the file you download either is an ISO file, or contains one (in the case of ZIP and RAR archive files). Never run or download any files with the EXE extension. Enter USB mode (as described above) and connect the PSP to your computer. Copy game files from your computer to the PSP memory stick folder to load them onto the system. Play your new game by going to the "Game" menu and selecting the game that you want to play from your memory card.

TL;DR in Vietnamese:
Nhận thức được hành động của bản thân. Tải game PSP. Chuyển game từ máy tính sang PSP. Chơi game.