You may want to modify the files and folders you are backing up, this can be done as follows.
Login to the backup client and click On Backup Sets
Select the backup set you wish to modify
Click Source, then either modify the selected tick boxes for Desktop, Documents Favorites etc, or click on "I would like to choose the files to backup"
Here you can modify your backup selection. Simply navigate to the files / folders you wish to select or deselect, then once finished, click OK
Then click Save.