The first step toward controlling what an Admin can do or see is to create a Role with specific permissions. Every Role has a set of permissions tied to it, so you can reuse the Role for multiple Admins. To edit an Admin User's role and/or permissions, follow these steps.
Step 1 - Access Admin User's Profile
Go to the Admins Page (My Company > Users > Admins). Edit an existing Admin's permissions by clicking on the pencil icon beside the Admin User's name.
Step 2 - Create New Role
Scroll down to Role & Assignments. Click on either "Role" or the current Role to show the Role Management window. If no Roles have been created, click the "+New" button. If there are Roles, click the plus button to add a new one.
If you don't need to create a new Role, skip to Step 3.
Step 3 - Select Permissions
Add a name for the new Role and select which permissions you want to provide to the Admin. There are 29+ permissions available for Admins. These permissions are described in more detail in this support article.
If you are editing an already created Role, you can select or deselect the permissions, then click "Save" to save the new permission.
IMPORTANT NOTE ABOUT EDITING ROLE PERMISSIONS:
Be careful when editing an Admin user's role. If you change a main Admin role, that role will be changed for EVERYONE who has the role, not just for the person you are editing! If an Admin user needs different permissions, create a new role for that person.
Step 4 - Save & Assign Role
Click Save and assign the role to the Admin User by checking the box beside the Role.