Add to Chrome.
Click 'Add extension' above.
The installation process should take less than a minute.
Next, you'll Create an Account.
You might also find your answer in the LastPass Enterprise Manual.
How do I add user groups to a policy?
When you create the Policy from your Enterprise Admin Console, select Inclusive List of users (for whom the policy applies to), and under the G listing in the alphabetical list of users, you will see a list of all the user groups you have created. You can then add the group to the policy as you would an individual user.