Instructions
Navigate to the YoYo games website (link in Resources) and download the latest version of Sonic FGX.
Extract the archive that you have downloaded to the folder of your choice.
Place the custom character file (in GIF format) in the same folder as the game files. You can create your own custom characters using a GIF editing program or download the files for free from sites such as Sonic FGX Custom Characters (link in Resources.)
Double-click the "Sonic Fgx.exe" executable file to launch the game.
Press "Enter" once the game has loaded and then highlight "Main Game" using the arrow keys.
Press "Enter" and then press "Z" once Sonic is displayed on the character select screen.
Enter the name of the custom character file located in the game directory and then click the "OK" button. For example, if the custom character file is named "my_character.gif" you would enter "my_character" (without the quotation marks) in the name entry box.
Enter a name for the custom character and then click "OK." The character name can be different from the file name but must be in all caps with no numbers.
Press "Z" to start playing the game with the custom character that you have uploaded.