Normally DSP is recognised automatically simply by having the DSP present on the databus.
This can be tested and verified with NavCoder - send the Device Status Ready command from DSP to LOC and the DSP option suddenly appears in the menu

Aux-In is available only from a certain firmware version of the radio, thus if you do not have Aux-In on your radio, it is likely the radio is too old. But check the Service Menu if any options exist to disable it :-)