AMPforWP is one of the most popular AMP plugin for WordPress users. But on the free version, there are some limitations like, you cannot add sticky ads on your amp page.
But here is, the way where you can easily ads STICKY Ads on your amp page like this.
Follow the below steps -
Step-1 At first visit your WordPress dashboard and then click on the AMP option.
Step-2 From the AMP dashboard click on the SETTINGS option and under this option click on the Advance Settings link from the sidebar.
Step-3 Now add this code
<script async custom-element="amp-sticky-ad" src="https://cdn.ampproject.org/v0/amp-sticky-ad-1.0.js"></script>
in the Enter HTML in Head section.
Section-4 At the end you have to add your Adsense code this is format
<amp-sticky-ad layout="nodisplay"> <amp-ad width="320" height="50" type="adsense" data-ad-client="ca-pub-123456789" data-slot="98765432"> </amp-ad> </amp-sticky-ad>
in the Enter HTML in Body section.
Congratulation, your sticky ads now showing on the amp page. Hope this will help you.
For any official reference you may visit, https://ampbyexample.com/components/amp-sticky-ad/