First steps
Popup explanations

note
Tabs will only show in the tab selector if they are in the list of supported platforms
Guided test
1 - Head to this video
2 - Click the extension in chrome's top bar to open the extension popup and select the tab
3 - Press the START button
The preview field should now show the title and the author of the video
4 - Keep the music playing and copy your Overlay Link from the extension settings and paste it into a new tab in your browser

note
OBS simulates a browser open on your Overlay Link in order to display your overlay onto the stream