Before you can start playing Resident Evil 4 on PPSSPP, you'll need to download the game in ISO format. There are several websites that offer PSP game downloads, but be sure to only download from reputable sources to avoid malware and viruses. Some popular websites for downloading PSP games include:
If the fan-made PSP version does not satisfy your needs, you can play the full, original versions of Resident Evil 4 on Android using more powerful emulators: Download Game Resident Evil 4 Ppsspp Iso