Can someone please teach me how to do that, or at least send me to a link to a forums or tutorial on how to do that? Thanks!

Oh, that's easy!

1. Find the files which include textures you want to modify [OpenIV]

2. Extract them [OpenIV]

3. Open them with Texture Toolkit

4. Extract the textures you want to edit [TextureToolkit]

5. Edit the textures

6. Import them (IN DDS FORMAT) to the corresponding files [TextureToolkit]

7. Don't forget to save the files [TextureToolkit]

8. Return the files to their place [OpenIV]

This is for GTA 4, not GTA 5. How do I edit the textures for GTA 4?

Edited October 17, 201510 yr by MegoGaming

Aaaaa sorry

OpenIV is enough for such work. Although, there are still some files with embedded textures and you will need to export them in Open Formats.