To generate the reports of a Revit model, open that Revit file and click on the Activate menu from the Radar panel. Now select the folder where reports will be saved in the Sync Report Directory, and click on the Activate button (the toggle moves to the right and it becomes blue). After this every time the Revit model is saved or synchronized a new report will be generated. Click then on Ok to save the changes or Cancel to abort the operation.
Bear in mind that it is also possible that instead of choosing a folder to save the reports, from the Activate menu the folder is created by typing the correct path and name for the folder. After saving or syncing the file, the folder for the reports will be automatically generated, even if it did not exist before. Just remember to use the correct convention to create the path and the folder, for example: