AMD opens in a new window each time, if you wanted to add it as a tab you can do one of two things.
1. RIGHT CLICK on the top of the window and hit SHOW AS TAB.
2. On your tools bar on the top choose TAB and select SHOW AS TAB.
Either of these options should convert the window into a tab you can drag into your Google tabs to have them all on the same window and switch between tabs.