Icon Chooser dialog shows up when you edit the Icon property for widgets
that support icons. These are Icon, Button, Label, Shape, Menu, etc. So
add for example Icon widget to your screen and then change its icon in
Properties View. The Icon Chooser will appear then and you'll be able to
select Glyphicons too.
Let me know if you need more assistance.
Patrik04 Apr 2014
Got it. I was using Bootstrap widgets, and they don't seem to have icon support. Thanks.