Sync audio to Multicam sequence

[Dylan28353174o1ay]

Hi there I have a problem syncing my audio to a multicam sequence. Currently I am in an editing class where the instructor wanted us to synchronize the 3 cameras by their In points. This part works fine, but when I bring in the asynchronous audio to pair with the multicam sequence the synchronize audio portion is greyed out. Not sure if this matters but the in camera audio has two tracks of sound on audio track one. 
I am unsure how to proceed and correct this problem. 

[RobShultz]

If I'm reading this correctly you'd also be using an in point on the audio to sync and wont need the synchronize by audio.