You don't need to modify the database, just the php files that belong to phpbb. There is documentation that comes with it. Read it carefully. If you do not have any other mods, such as a clean install of the forum software. You can copy the php files that come with the mod to the correct locations. Once that is done just verify line by line of the documentation make sure everything is correct. When reading the documentaion, make sure that word wrap is turned off. If you don't it can look like some some of the text belongs to the next line, when in fact is does not.
Other than that, you should be set to go. There is a thread on phpbb's forum dedicated to this mod. Odds are you will get more detailed help, than you would here, because everyone reading that thread is already going through or has gone through the process your about to. Besides the author of the mod visits that thread.
If I can help, I will, but I do not know very much about php yet. But I was able to get it running. So I am sure you can too.