First you have to copy the code to the characters that you want to use for the fusion (you can also use it for two different characters). Take a look at the notes between the stars. The code is included together with the study example.
The example is designed for fusing two Justins to Julian, so there may be some picture-errors. In this case, you have to modify the pic-numbers, too.

2) Transform
You also have to modify the character you want to transform into because you'll have to use state: 80??. First, test the fusion and see if there are any graphical errors after the transformation. If yes, you can download "Random Criminal" from the download section - all figures are changed so you can do this there (it's okay to copy these modified figures from Random Criminal and publish them under your own name, but I would be happy if you made a note of this in the readme).

3) Further Notes
- Fusion between enemies is possible
- State: 13 used for Fusion Run (same function as state: 18)