For instructions on how to edit a Contact’s Interest Level rating from the Contacts section of the platform, see How do I manually adjust the Interest Level rating of an individual contact?
Under the “Preferences” tab, find the “Auto Adjust” option, and click to unselect/clear the checkbox if it is not already blank. If you disable Auto Adjust, you can then manually change the Interest Level. When you have made your adjustments, click "Save".