In order to set up base configurations for Magento 2 Open Graph Module please go to Stores > Configuration > Magefan Extensions > Open Graph.
1. Enable an extension choosing correspondingly Yes in Enable Extention select box.
2. In a Default OG Image, you can set Open Graph image by default. The chosen image will be used for a page if it is not redefined, for example in product settings.
3. The Open Graph description can be set by default in a Default OG Description.
Once you have finished with all of the configurations don't forget to press the Save Config button.