There are two files and one directory in the download that need to be installed, the rest are there for documentation. Installing them is simple, feel free to rename the members.php file to whatever you want, and copy it to your main bbPress installation directory. You will want to add a link to this file in your template.
The bb-user-directory directory needs to go into your my-plugins directory. If you dont have one, you can create it so that it lives alongside your bb-plugins directory. Alternatively, bb-user-directory can be dropped directly in to your bb-plugins directory.
Lastly the userdirectory.php file needs to be dropped into your active theme directory.
The files are packaged in the correct directories, so you may be able to unzip and upload directly to your bbPress installation, assuming you rename the "your-theme" directory appropriately. Oh, and don’t forget to Activate the plugin!