Most downloads are ZIP or RAR files. Use an app like ZArchiver to extract the .iso or .cso file from the archive.
The process is relatively straightforward and involves three main parts: setting up the emulator, acquiring the game files, and then configuring everything. how to download gta 5 ppsspp iso file for android
A legitimate PSP game is always an .iso or .cso file. If a website forces you to download an .apk file to play a PPSSPP game, do not install it. It is likely malware. Most downloads are ZIP or RAR files