The administrator privileges are adjusted in the account settings screen.
Open the Start Menu, choose Settings and then Accounts.
Find the Family & other users section. Click on the account to which want to provide admin privileges.
Choose the option labeled Change account type. Open the drop-down list, select Administrator then OK.
Once the administrator account has been set, it's time to test it. Log into the new admin account and try to launch something as an administrator to see if it works.
If you want to remove admin privileges from a given account, the setting can be reversed from the same menu.
Go to the Start Menu, Settings then Accounts. Locate the Family & other users section and click on the account that no longer needs to be listed as an administrator.
Click on Change account type and use the drop-down to remove the admin status. Click OK. The account will no longer be considered an administrator account.