I've looked everywhere for the 3 bars on top left. I'm apparently missing something, lol Can't find them.
It depends on whether you are on a mobile phone in vertical/portrait position, or on a wider screen. The website adjusts to the size of your display and changes the layout a bit to best fit the device used.
If you are on an eider screen and see you avatar image in the upper right. Clicking on that gives you options (I have more than most because I’m an admin). But you should see Account details, where you can edit most things about your profile. You can also select “Signature” if that is what you’re looking to edit.
I’m using a large iPad, so mine is closer to what a full computer browser would see.