Here's how to replace individual CSPs. From the CSP thread:
- Download DTW (download link above).
- Open your ISO in DTW (via drag-n-drop or the File menu)*
- Click on the Disc Shortcuts | 'Menus' link
- Select the MnSlChr.usd file, and click on Browse Textures
- Find and select the texture you want to replace
- Drag-n-drop the new texture onto the GUI
- OR - Right-click -> Import, and navigate to your new texture
- File -> Save (or press CTRL-s)
Alternatively, if you are using a mod I'm assuming that you downloaded and already altered MnSlChr.usd file. In that case, you would use this guide:
https://ssbmtextures.com/tutorials-importing-dat-files/. That link uses a stage file as an example, but the same principal applies to any file in your iso. The only difference between the steps provided and what you will do is instead of clicking Stages, click Menus and once you find the menus you'll replace MnSlChr.usd (The CSS / Character Select Screen) instead of said stage.
Let me know if you have any issues.