In XenForo, create an API Key by navigating to ACP > Setup > Service providers > API Keys > Add API key and for Key Type choose Super user key. You can also use an existing API Key that is a Super user key. A Super user key has all scopes.
In WordPress, go to Settings > XPress Forum User Bridge.
Enter the board URL.
Enter the API Key from XenForo.
Choose the other settings.
Save your changes.
In XenForo, go to Admin Control Panel (ACP) > Setup > Options > [TH] XPress Forum User Bridge.
Enter the root URL of your WordPress blog.
Enter the WordPress API key that was displayed in WordPress Dashboard > Settings > XPress Forum User Bridge.
Choose your other settings.
When finished, choose save.
XPress Forum User Bridge is then set up.