How to Prioritize visible content

This is the message i a getting on running test

Your page requires additional network round trips to render the above-the-fold content. For best performance, reduce the amount of HTML needed to render above-the-fold content.
The entire HTML response was not sufficient to render the above-the-fold content. This usually indicates that additional resources, loaded after HTML parsing, were required to render above-the-fold content. Prioritize visible content that is needed for rendering above-the-fold by including it directly in the HTML response.

None of the final above-the-fold content could be rendered even with the full HTML response.

Please help