Jenkins needs to know where your Maven is installed

Jenkins 2.1 maven project
Within system configuration there is no where to set where maven is (I am running mint Linux and it is installed in /usr/bin/mvn - default location).
Under global properties is a Tool Location section but this only allows “(Git) default” as the value. It is the only value in the dropdown list. Adding an extra location gives the same option.
So rather confused - what am I doing wrong?