You must be a windows guy. What you call administrator we call root :). Ok, here's the answer

If you want to run a specific command with elevated privileges you can simply prefix the command with sudo for example

sudo nginx -t

But if you want to login as administrator, say you have a series of tasks you want to run all in elevated mode, then you can

sudo su

and when you dont need the elevated mode anymore

exit

Note: you will be asked for your password when attempting command elevation and when you succeed your prompt will have a # instead of a $