Log in to https://myonecloud.com/

Click on the Phones navigation icon.
Click the gear icon next to the phone whose buttons you wish to edit.
Click Yes in the confirmation window.
You are now in the button builder. Here, you’ll see an image of your photo with the buttons you can program.
Note: Buttons 1 and 2 should always be set to your Line Appearance. You will not be able to change these buttons. You may have additional buttons (such as park) programmed per your company’s configuration and it’s not recommended you change these. Click on any button (or number on the right) and you will see “Select a Feature.”
Line Appearance – line registration to the device.
Shared Line Appearance – adds a shared line that can be added to multiple devices.
Users (BLF) – Allows you to see the present status of another extension. Can be used to call the extension.
Call Park – Parks the active call and also uses the button to retrieve the call previously parked.
Speed Dial – This allows to speed dial a specific destination.
Queue Toggle – Logs in and out of queues.
When you have finished editing your ELF keys, you hit the up-arrow next to the Save button and press Save and Resync.
Your phone will sync to show the new buttons. (Your phone may also reboot during the process.)
Tip: You can drag and drop configurations to re-order their assignments.