Step 1 - Go to the switch user page
From the main screen, press on the user icon in the top left.
Step 2 - Press on the user name
Now press on the username (not the image... just the name) of the user that you want to delete. You will now see a menu pop up with multiple options. Press on "Edit user"
Step 3 - Change the name
Just press on the username to enter a new name.
Step 4 - Press Save
Press on the save button to save your changes.