You can add or remove a reference from a folder by checking the box next to the reference. You can select multiple references at once.
To add a reference to a folder:
1. Check the box next to the reference(s).
2. Select Assign to Folder in the top left corner of the tool bar (it will become clickable once you select a reference). Select the folder where you'd like to add your reference(s). You can either select a preexisting folder or create a new one.
3. The reference(s) will be automatically moved to the location that you have selected.
4. You will see the numbers after the folder name change as more items are added to a folder.
5. You can also see which folders any reference is in from the All References view. In the reference record, the folders are in blue underneath the article title.
To learn more about RefWorks, consult this guide:
