Please how do I correct this permission error

[uchenna0]

You don't have permission to access /forum on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

 

[Gouri]

You don't have permission to access /forum on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

Check the folder permissions whether they set to 0755 or not. in your file manager.