Singleplayer Installation
Follow these steps to install the mod for singleplayer:

Ensure you have Grand Theft Auto V installed via Steam, Rockstar Games Launcher, or Epic Games Store.
Download the Liberty City mod files:
FiveM-compatible files (optional)
Singleplayer files
Singleplayer HD files (for enhanced graphics)
Download ScriptHookV and extract the files.
Open the Bin folder from the ScriptHookV download and copy the following files:
dinput8.dll
ScriptHookV.dll
Paste these into the main directory of your GTA V installation (whereGTA5.exe is located).
Download OpenIV and install it. Set it up for Grand Theft Auto V.
In OpenIV, go to the Tools menu in the top-left corner and open ASI Manager. Install all three options that appear.
After installing ASI Manager, you should now have a mods folder in your GTA V directory.
Return to the Tools menu, select Package Installer, and follow these steps for each part of the Liberty City files:
Select the PART 1 file and install it to your mods folder.
Repeat this step for each subsequent part (e.g., PART 2, PART 3, etc.).
Launch GTA V. If installed correctly, you should see "World Travel" displayed in the corner of the screen.
In-game, press F11 to teleport to Liberty City or travel to the blip marker at LSIA.
Important Notes:
If the mod doesn't work, ensure you've downloaded the ASI hotfix from the appropriate source.
Make sure there are no conflicting maps or mods installed.

Installation Video
https://youtu.be/Ggm5gzCd9Ig