You're right to connect your transformer to the Power terminals. However, the timer doesn't place any voltage across the contacts. Use terminals 4&5 as a 12VDC supply and connect the contact in series with the solenoid. Check out this picture of an SSR as a reference. Remember though, you're using the timer terminals 4&5 as the power supply. Also here's a poorly typed out connection guide for the NO contact: 4->8, 7->SV+, SV- ->5.