You can enable Rate my Post – WP Rating System Compatibility in Schema and Structure plugin by just enabling the option. It’s pretty easy for you to set up because it works out of the box.
Step 1: Go to WordPress dashboard -> Structure Data -> Settings -> Compatibility
Step 2: Please refer the below steps and checked the box of Rate my Post – WP Rating System in the Compatibility section of the options panel and save it.

whatever schema type you have added (which support aggregate rating) inside that aggregate schema markup will be added for that post.
The Output of Rate my Post – WP Rating System

In the source code, JSON schema markup will be added like below the screenshot.

After that, you need to check the schema whether it’s validated or showing error in the Structure data testing tool.
Structure data testing tool: https://search.google.com/structured-data/testing-tool
That’s it for this tutorial!
We hope it helped you. If you have any feedback or questions or do you want us to create compatibility for any other schema type which isn’t listed in our plugin then you can request us we will surely implement it as soon as possible.
Just contact us here and we are always available for you.