The admin menu that was in game has been broken and got removed by the devs but is due to make a comeback in an update.
For the time being you will have to use RCON controls and RCON software which there are plenty of (a few are listed in the reference link below (REF.1)
All servers are setup with a port for RCON, if you need help making sure your RCON config is correct (REF.2) then please let us know.
Location for both Shack and PC: /Pavlov/Saved/Config/RconSettings.txt
REF.1: http://wiki.pavlov-vr.com/index.php?title=Dedicated_server#Admin.2FModerator_list_.28optional.29
REF.2: http://wiki.pavlov-vr.com/index.php?title=Dedicated_server#Rcon_Overview_and_Commands