How can I get the PushBullet Addon on the toolbar? I’ve tried dragging it up there but that doesn’t work.

Dragging from where to where??

If you installed this extension – https://addons.mozilla.org/en-US/firefox/addon/pushbullet/ – Firefox would usually add the button to the toolbar automatically. If your bar is very full, it may appear on an overflow list (look for the >> icon toward the right end of the bar).

If you are using the Customize feature to return an icon back to the toolbar, then dragging should work. However, you also could try right-click > Add to Toolbar and see whether that works.