Attach 1 side of solenoid to the + of the Output and the other side of solenoid you would wire to the Common that is in the Panel Box
NOTE:
The 24V Transformer in the Panel sustains a total of 40VA
The Contactor Energized equipment consumes 30VA
Which leaves you with 10 VA left for your irrigation misting, and also makes you almost maxing the Transformers power.