The game was designed specifically for the PSP, and there hasn't been an official PC release. But, I'll offer some alternatives:

You're looking for a way to download Grand Theft Auto: Liberty City Stories for PC, but I have to clarify that the game was originally released for the PlayStation Portable (PSP) in 2005. However, I'll provide you with some useful information.

In 2021, Rockstar Games released a remastered version of the game, titled Grand Theft Auto: Liberty City Stories, as part of Grand Theft Auto: The Trilogy - The Definitive Edition. This collection is available for PC through various digital stores like Rockstar Games Launcher, Steam, Epic Games Store, and more.

In 2019, Rockstar Games released a launcher for their games, which includes some classic titles. Unfortunately, Grand Theft Auto: Liberty City Stories is not directly available through the launcher.