Tags can be added to leads to associate desired information which will help to classify the lead better. You can add tags to a lead from the pipeline itself or its respective page.
1. Adding tags directly from the pipeline view
Click on the tag icon on the lead card (at the bottom centre).
A list of all possible tags for that pipeline will appear. Select the desired tag(s) and Click on Update.
2. Adding tags from the lead page
Go to the Lead Details page and click on Edit Tags (as highlighted below).