when you have the menu bar showing,(right clicking in the top area of firefox will give you a context menu , menu bar is first in the list)
then select view/sidebar/bookmarks as in the pic ,they will then show on the left.
if you add the bookmarks button to the top row next to refresh ,home etc then you can open and close the bookmark sidebar at the click of a button.
You can add the button by right clicking the top area of ff and select customize and then in the window that opens drag the bookmarks button to the area you want.
there are two buttons one is for the sidebar and one is for a bookmark pop up. be sure to play with them to get the right one.