This post gives Honeywell RTH9580WF WiFi setup directions for this touchscreen smart thermostat. Use this routine to get your thermostat up and running for the first time in your home. Or this also works to set it up to a different WiFi network.
Perhaps you changed the name of your home WiFi network. Or perhaps you changed your WiFi router but didn’t set your new router’s network settings exactly as they were before. Or, you may want to set up the t-stat to a new access point in your home. For all of these cases, you can setup the thermostat to WiFi by following the instructions below.

Honeywell RTH9580WF WiFi Setup: Step by Step
For sure, Honeywell really improved the WiFi setup routine for this smart t-stat. Indeed, you no longer must set it up via a tablet or phone to change the network settings. Instead, you can now set up the entire WiFi profile via the RTH9580WF touchscreen menus. Here’s how.
1. Enter WiFi Setup mode
First, switch from normal to WiFi setup as follows. Press the Menu button at the top right of the Home screen, as shown above.
Then, scroll with the arrow keys at right, through the main menu. Stop scrolling when you see the Wi-Fi Setup button, as shown next.

Next, press the Wi-Fi Setup button, circled in red in the above pic.
The Wi-Fi Setup screen then displays, as shown next.
Note that we have blanked the t-stat MAC address and CRC values, to preserve its anonymity. Also note that normally, this screen shows the status of the connected WiFi network. But here, the OurHouse1 network is not in range (no signal). So we’re going to discard the OurHouse1 info. Then we will replace it with an in-range WiFi network in the following steps.

2. Disconnect the T-stat from its Current WiFi Network
Skip this step and move to step 3 if you thermostat is not currently on a WiFi network. It is probably not if this is first time setup.
Then press the Disconnect from Network button.
The WiFi Network Disconnect Confirmation screen appears, as follows.

Press the green Yes button. After a pause, the system lets you know that it disconnected from the old WiFi network, as shown next.

Then, press the green OK button in the lower right corner of the screen. After the press, this takes you back to the main menu, as shown next.
3. Find the WiFi Setup Button to Continue with Honeywell RTH9580WF WiFi Setup
From there then, use the UP and DOWN arrow keys to scroll through the menu to the Wi-Fi Setup button.

4. Tap the Wi-Fi Setup Button
Then, press the red-circled Wi-Fi Setup button.
When no network information resides in the t-stat, pressing Wi-Fi Setup starts a scan for in-range WiFi networks.
Then, a brief message displays, showing that the network scan is in progress.
Next, the RTH9580WF lists the in-range WiFi networks it found, on its Select Wi-Fi Network screen, as follows:

5. Find your Desired WiFi Network
Then, tap the network in the list to which you wish to connect the smart t-stat. So in our case, we’re connecting to the 937T681J4059H_2G wireless network.
The WiFi Password Entry screen then appears, as follows.

6. Enter WiFi Password if Asked For to Continue with Honeywell RTH9580WF WiFi Setup
Next, use the displayed virtual keyboard to enter your password. To enter numbers and punctuation characters, press the ?123 key. Why? Because this switches the keyboard to number entry mode.
The password characters appear as you type them. So do this when no non-trusted folks are looking.
7. Connect to the WiFi Network you Picked
When you’ve finished entering the password characters, press the green Done button.
This WiFi t-stat then tries to connect to the chosen WiFi network. While reconnecting, it displays the following screen.

Then, if no errors happen, the system reconnects to the selected WiFi network.
Next, it shows the following screen. Here, it displays the name of the wireless network that the t-stat now connects with.

8. Register your Honeywell Thermostat Online for Remote Access
Next, press the green OK button.
Then, the Register Online for Remote Access screen then appears, as shown next.
Now perhaps you already registered your WiFi t-stat. If so, then you need not register it again, so long as you have not unregistered it. Note that setting up to a new WiFi network does not unregister the t-stat.

Then, press the green Done button.
The system then returns to the Wi-Fi Setup screen. But this time, the connected network info appears, as shown in the next shot.

Next, press the green Done button. Then, the t-stat takes you back to the main menu, as shown below.

Then from there, press the Home button at the top left corner of the Main Menu screen. This to returns you to the Home screen.

9. Honeywell WiFi Thermostat Setup Done!
Finally, your Honeywell smart thermostat is now working on the new WiFi network. So you’ll see that when the outdoor temperature and humidity settings update soon after.