There is no way to access the Firefox settings in the Android app! Android hides the menu icon on my phone, but not my tablet. My phone has no hardware menu button. I found an article saying that if you long-touch any Firefox button, you can access the settings. The only button available to me is the tabs button, which when pressed or long-pressed only opens the tabs. This is a development setback imo, that you cannot simply access settings by swiping or something.