Here is how to correctly install Avatar Upload.
The "Additional Info" is not too detailed.
Here is the instructions on how to get the plugin (currently) on your bbPress site:
1. Download and upload the plugin to your bbPlugins directory.
2. Activate the plugin in the bbPress Admin section.
3. Follow the file movement instructions:
In the "additional-files" folder (inside this Avatar Upload plugin directory) there is several files. These need to be moved elsewhere.
- Move the entire "avatars/" folder to your bbPress root directory. (Including the "default.png" inside.)
- Move the "avatar-upload.php" to the bbPress root directory.
- Move the "avatar.php" (inside the "my-templates" folder) to your template(s) (theme(s)). Example: Move "my-templates/avatar.php" to "forums/bb-templates/kakumei/" (So it is like "forums/bb-templates/kakumei/avatar.php".)
I hope this helps someone :D