The quick way is to hold down <Shift + Control> and then press B Also, look at the top of the Firefox window. If you see the Firefox button, then left click it for its menu. If there is a bar instead one of the buttons is for bookmarks. Remember one very important thing; the dumbest question anyone can have is the question that is not asked.

Which bookmark icon are you referring to?

Is that an icon one the Navigation Toolbar or possibly on the Bookmarks Toolbar or do you mean the favicons (website icons) that appear next to a bookmark on the Bookmarks Toolbar?

What action did you get when clicking this button?

Note that some icons may not appear when the menu bar is visible or possibly the Bookmarks Toolbar.

• Firefox menu button > Options
• View > Toolbars (press F10 to display the menu bar)
• Right-click empty toolbar area

Use Toolbar Layout (Customize) to open the Customize window and set which toolbar items to display.

• check that "Bookmarks Toolbar items" is on the Bookmarks Toolbar
• if "Bookmarks Toolbar items" is not on the Bookmarks Toolbar then drag it back from the toolbar palette into the Customize window to the Bookmarks Toolbar

• if missing items are in the toolbar palette then drag them back from the Customize window on the toolbar
• if you do not see an item on a toolbar and in the toolbar palette then click the "Restore Default Set" button to restore the default toolbar setup

See also:

• https://support.mozilla.org/kb/How+to+customize+the+toolbar
• https://support.mozilla.org/kb/Back+and+forward+or+other+toolbar+items+are+missing

As to the bookmarks icon, move your mouse to the top of the Firefox window, to the same level as the tabs bar. Right click and select customize. If you don't see this, reposition the mouse and try again. Once you open customize, you will see many icons. One should be bookmarks. Mouse on top, hold down the right button, move it to where you want the icon, and then let it go.