Need to know where to tap into for a sub and amp install. Searched but couldn't find

[Bruno_s4]

Have base model Concert sound system and want to install a JL Audio 500/1 and JL-Audio-CVS112RG-W6v2 subwoofer/box and need to know where to tap into to get a clean audio line for the sub.
I think I can figure out the power but need a trigger wire as well.

Searched but found more subwoofer replacement information.

Thanks