There are various means for excluding files or locations from backup. Only the first method will actually delete all file versions from the backup, the latter methods will only exclude newer versions from being added.
Right-click a file/folder → Point to Genie Timeline → Remove from backup. This will also delete all version of the file in backup.
Drag/drop files to No-Backup Zone located on the Desktop.
Auto-Exclude to exclude full file and folder paths.