See here for more information.
Before starting open the dev tools console (on a Mac cmd-option-i)
- Open the Settings panel within the dev tools console (click gear icon on right side)
- Check “Show ‘Emulation’ view in console drawer (looks like you have already done this step) and close screen
- Switch to the sources tab of the dev tools console
- Press Esc to bring up a screen that slides in from the bottom
- Select the Emulation tab on that second screen
There is also a note in the link above stating:
Note: Emulation tools within DevTools were previously contained within
an Overrides pane inside the Settings panel. The Emulation panel is
the new Overrides pane.