1. Go to the Dashboard of the domain in question
2. Scroll down to the keyword section. Select the keyword(s) you wish to add to a group. The box at the top of the keyword section can be selected to check all keywords.
3. When you are done selecting the keywords you want to add to a group. Look at the bottom of your screen. At the bottom of you screen you be presented multiple options, click the label icon to assign a group to the selected keywords.
5. Write the name of the group and assign.