The Keezel only has one button, so turning it on and off is very simple: just long-press the button for about 3 seconds to turn it on and push it (no long-pressing needed) to turn it off.
When you turn the Keezel on, the light on the device turns blue and after a short while, starts rapidly blinking green. While the light is blue or blinking green rapidly, the Keezel wifi will not be visible in your list of available networks. Once the light starts blinking green steadily, that's when you'll see the Keezel Wifi and be able to connect to it.
When you turn the Keezel off, the light turns off as well.
If for some reason, the light is stuck on blue and does not turn green (even after you've waited for 1-2 minutes), you will need to long press the ON/OFF button for about 10 seconds until the Keezel (and the light) turns off.