Again, page 166 details operation of the TIMER and how to set a switch to turn it on or off. It is not a general switch-setting instruction.

If you have a device that turns something on and off, it needs a control signal from the receiver that has two states: All one way, all the other way. You can select a channel in the Function section of the Linkage Menu and assign an aux channel to it. Then select a switch to operate that channel. The switch will then move the channel to one extreme or the other. If you connect a servo to that channel, it will move from one extreme of its travel to the other when you move the switch. An electronic on/off device uses the same signal, it just replaces a servo that physically moves a switch in the model. With some devices, you'll need to adjust the endpoints so that the device operates properly.

A glow plug device like a Switchglo is just plugged into any available channel in the receiver. You would take a channel, such as channel 9, assign it to an aux channel in the function section of the Linkage Menu, and then assign the desired switch to operate that channel. You're done.