Just an additional thought:
As has been mentioned already, Firefox (and every browser in the world except Internet Explorer and Edge) uses the term 'Bookmarks' rather than 'Favorites' (with that horrid US spelling!). If you don't see 'Bookmarks' at the top of your page, along with 'File', 'Edit', 'View, etc, it means that you've not got the Menu Bar enabled. To turn it on simply right-click at the top of the page and put a tick in the relevant box.