Download the Portal 2 crack fix for the SKIDROW version from a reputable source. Make sure to download the correct version that matches your game version.
Before applying the crack fix, ensure that your game files are intact and not corrupted. Check the game directory for any missing files or folders.
Extract the downloaded crack fix to a folder on your computer. Then, copy the extracted files to the game's installation directory, usually located at C:\Program Files (x86)\Steam\steamapps\common\Portal 2 .