how to call TL manager 2016 as administrator

[Michael Berger]

Hi,
I have /usr/local/texlive/2016/bin/x86_64-linux
I can open the GUI as user in a console using 'tlmgr gui' but have the 
buttons grayed out.
I am told to run this program as administrator.
I tried both sudo 'tlmgr -gui' in an user console and 'tlmgr -gui' in an 
administrator console but keep getting 'command not found'
Please, can somebody advise what to do?
Michael