Turning my comment into an answer:
"+
is the register that refers to the system clip board, this works for Linux as well as Windows (this is what I was able to test). You can copy to it with the "+y
key strokes, given that you've previously selected something. To copy the whole line you're on, you can use "+yy
(used as an example, you might have to google other cordes). You can then switch to firefox, with alt + tab
for example, and then select the address bar using Ctrl+L
, and paste using your system's paste shortcut, most likely Ctrl+V
.