Type the terms and press the "Search" button. In the Items found section will be displayed the list of posts/pages that include the term. Select the posts/pages to associate manually.
Go to the post's edition and press the "-" symbol from the items manually related.
Type the terms as tags associated to the post.
You only should replace the images for icon_on and icon_off, located in "/wp-content/plugins/cp-related-posts/images"
You only should increase the similarity percentage, from the settings page of plugin.
Note: The above is a safe process, the plugin's data and settings won't be lost during the process and will appear again after installed the pro version.
Alternative Installation Method:
The upgrade instructions are exactly the same instructions mentioned above but be sure to make a backup copy of your current files if you have made custom modifications to the files or translations since the files will be overwritten.
After upgrading the plugin remember to clear your browser cache.
The free version must be deleted before installing the pro version.
If you are upgrading the pro version to a new version you should also remove the previously installed version.
This is a safe step, the plugin's data and settings won't be lost during the process.
Another alternative is to overwrite the plugin files through a FTP connection. This is also a safe step.