After you've set up an ad group, you may want to add additional keywords to boost clicks and improve performance. Adding new keywords can help you generate more traffic from your top performing ad groups, or it can help you boost clicks on ad groups that are not getting enough traffic.
Prepare the list of keywords you'd like to add to your campaign, if you have specific terms in mind. If not, AdWords will automatically suggest some new keyword options based on your existing keywords.
If you already have a list of keywords you'd like to add to an existing ad group: