To remove a folder from backup, open the Onlime application and select the folder. Then click on Delete folder. You will be asked to confirm the deletion.
When you delete a folder, it will be placed in the Trash. Here it will stay for 30 days, after which it will be deleted permanently.
Please note that you cannot delete a folder from backup via the Onlime website. It has to happen from the Onlime application.