As an admin you can add users to your account who have the ability to impersonate other users. Before you can do this you must have already created a role that has the impersonate access type.
1. Go to Account Settings > Team members
2. Click "Add team member"
3. Enter the details for the new user and under "Permissions" select "Specify role".
4. Next select the role which you have created with the "impersonate" access type.
5. Now you will see the "Impersonate users" section. Start typing the name / email of each user that you want to allow this user to impersonate and select the user.
6. Once you have selected all your users you will see them listed under the "Impersonate users" section.
7. Save the new user.
When this user signs in they will be required to select one of the users they have been given access to impersonate.