Help with Marantz NR1510

Trying to help a friend with New AV unit.  He ran his rega TT strait in to the phono stage fine.  Then he wanted to compare that to the external phono stage he has.  I told him to go into the audio in assignable 1 , 2 or 3 but when he tried that no sound.  Does he have to activate those inputs in the "audio in" section of the NR1510?