On first boot
After it boots all the way up the first time after you install, boot again. I dunno why, but you gotta.
Date & time
On the home screen, the very top middle of the screen shows the date, and time is displayed in large text above the four primary buttons mid-screen.
Network & Signal Strength
On the home screen, the top left bar on Zhone is the signal strength. The length of the blue bar compared to the black box it's in is how strong your signal is. No blue bar, no signal. Above the signal strength bar is your network name.
Battery life & some other stuff...
On the home screen, the top right bar is the battery remaining. The length of the green bar compared to the black box it's in is how much battery is remaining. Above the battery remaining bar should be a series of letters (b G1 w s). They stand for Bluetooth, GSM, WLAN and GPS, respectively. Small letters indicate "turned off", capital letters are for "turned on". If it says "no dbus" above the battery bar instead of no letters, try rebooting the phone if it doesn't go away after about 30 seconds.
Press the power button for 10 seconds to turn the phone off. Release and hold again to turn it back on.
Push the power button for 2 or more seconds.
Push the power button once, or receive a phone call.
Touch the button with the phone on it. Type in your number. You may have to backspace (using the left arrow) to remove the previous number you called. Touch the green checkmark.
Hold & hang up
It should switch to showing your number, with a hold & hang up button underneath. The hang up button does the obvious.
Returning to the main screen
After you hang up, it remains on the same screen, with the hold & hang up buttons blanked out. Above the number it will say "Release". You can just click the X on the lower right to return to the home screen.
The two left buttons on the bottom of the screen don't appear to do anything.
Of the four buttons in the middle of the home screen, the top right button starts a demo of a keyboard. You touch & drag to type characters. There doesn't appear to be a way to delete, and the characters can't actually be fed anywhere, so it's not good for much now.
Sometimes you'll see the background faded and four numbered buttons on the screen. Press 1, then 2, then 3, then 4 to unlock the handset.