[BirdOPrey5]

You need to install the Tapatalk software on your forum first as it says to in Step 1.

Step 1

Create yourself an account at http://www.tapatalk.com/plugin.php. Once you have logged in
to the website, you can download the largest version. If you are not sure you are
using the latest version. Download a new one from
http://www.tapatalk.com/download.php. You can follow the rest of the instruction
from tapatalk.com onward if you want. Otherwise read on:

Then follow the other steps in the first post to make sure it's all uploaded and working, including registering your forum with Tapatalk.

Only after you've done that do you worry about the iPhone app...then you basically just run it, choose your forum (or any other) and enjoy.