To do so you need to be an administrator yourself, begin with launching an elevated command prompt by doing the following:
In the search box, type cmd.
Right-click cmd.exe and select Run as Administrator. If done properly, the User Account Control window below opens.
Click Yes to run the Windows Command Prompt as Administrator.
From here you will want to copy and paste the following then hit enter:
net user administrator /active:yes
Now you will want to set the administrator password by typing the following into the elevated command prompt windows:
net user administrater newpasswordhere
Replace newpasswordhere with your preffered password for the Administrator account.
Now you should be able to log out and log back in as administrator.