There are a number of different ways to apply document tags. 

1. From the Documents view, right click on a document or folder of documents in the index and select Add Tag. You can also select multiple documents by holding down either Ctrl or Shift:


2.  From within a document, click on the Tags icon in the tool bar and select a document tag:       

3.  From the Search section, you can tag your results by selecting the tag button under Tools:

4. From the Notes section, documents that have been annotated can also be tagged using Tools: