How to Integrate the OfferWall ?
In your App's Overview section:

Click the orange Integrate button at right-most border of the screen, below the Actions column header.

This screen gives all the details you need to integrate the app.
You can see in the screenshot that the integration url is:
<iframe src="http://www.offerdaddy.com/wall/1249/YOUR_USER_ID/" frameborder="0" width="860" height="2400" ></iframe>
The ONLY detail you need to take care of is replacing YOUR_USER_ID by some string that helps you identify the user viewing the wall. It could be a unique ID generated by your APP, or simply the username of the user, for example: Michael00986
Sub IDs
You can pass up to 3 sub ids in your calling url like this:
<iframe src="http://www.offerdaddy.com/wall/1249/YOUR_USER_ID/s1/s2/s3" frameborder="0" width="860" height="2400" ></iframe>
And those sub ids will be returned in the Postback as &subid1, &subid2, &subid3
As you can see, the process is very simple.