If you're using Firefox in the 'normal' view (rather in full-screen mode) you should have a menu bar with 'File', 'Edit', etc across the top of the screen. It's that bar (in a blank space) that you need to right-click on.
If you've not got the menu bar it's either because you're in full-screen mode or because it's been disabled.
If there's absolutely nothing at all at the top of the page (not even a tab heading) then you're in full-screen mode. To toggle between the 'normal' and 'full-screen' view you normally press F11 but some laptops allocate an alternative function to 'F11'. If so, try pressing Fn and F11 together to get out of full-screen mode.
If you've got no menu bar at the top of your page, but you can still see the tab headings (and the word 'Firefox' with a downward-pointing arrowhead in an orange rectangle at the top left) then you're in the normal view but with the menu bar disabled. Simply right-click in the space at the top of your screen (between the tab heading and the 'minimize' box) to enable the menu bar and/or to find the 'Customize' option (which includes the option to 'Add New Toolbar')
Chris