To edit a user's permissions you must be an admin for the respective company. From here you will select the "Settings" section (for the desired company) as shown below.
Once you click into the "Settings" section you will immediately be directed to all of the users associated with your company (shown above).
From here, you will be able to click on a user's name and will be able to edit their permissions as shown below:
If you select the "Enable Admin Privileges" box the user will have the ability to edit all of the sections.