Uhh how about a little more detail? I installed it, but I have no idea how to open it in a tab. Unlike my other extensions, I don't see any icon buttons next to my URL bar.

EDIT: If like me, you're using a Mac, you can use Alfred to open Postman. I still have no idea where to find the extension (I have both the extension and the "packaged app", whatever the difference is, installed on my machine)

Hmmm, I don't know. When I install it on Windows Chrome, I immediately get an icon next to the URL bar. Sorry I can't be of more help.