bbPress enables you to set up forums on your WordPress install. bbPress was originally a standalone forum (bbPress 1.0) that integrated with WordPress (and the BuddyPress plugin) but didn’t reside in WordPress core.
bbPress is now a plugin for WordPress (bbPress 2.0).
You can install bbPress using:
Automatic Plugin installation
1. Log into your WordPress administration panel.
2. Go to Plugins > Add New in the network admin dashboard (on WordPress Multsite).
Or Plugins > Add New (on WordPress)
3. Under Search, type in bbPress into the search form and click the Search Plugins.
bbPress should be the first result in the returned list
4. Click Install Now.
5. Go to the plugins page in the Site Admin dashboard.
6. Click on Activate below the bbPress plugin.
Manual plugin installation using FTP
1. Download the bbPress plugin.
2. Unzip the file to extract all of the files into a folder on your hard drive.
4. Launch FileZilla (refer to these instructions if you are new to FTP).
5. Locate and open up the folder on your computer that contains the new plugin.
6. Upload the bbPress folder from your computer to /wp-content/plugins
7. Log into your WordPress install.
8. Go to the plugins page in the Site Admin dashboard.
9. Click on Activate below the bbPress plugin.