The Festos that have come in the Kit the past few years are 24v devices.
Solenoids connect to the Solenoid breakout, NOT the Analog Breakout.
Note that the Solenoid Breakout is shorter than the Analog Breakout, and the Solenoid Module has two rows of green status LEDs.
The Solenoid Breakout can be wired with either 12v or 24v directly from the Power Distribution Panel. Pick the right one for your solenoids.
The 24v Festo looks like this:
If you really have a 12v solenoid (not a Festo) then it can be wired to a Spike and controlled in code as a Relay.