So I managed to merge my dome according to the video. I had a bit of trouble the first time though with removing doubled vertices and I’m not sure if it was because I was switching in and out of edit mode during the process.
Is it a requirement to stay in edit mode the entire time your molding new shapes?
No, you don’t have to stay in one mode the whole time. Personally I switch between modes quite a bit when modeling as it helps to see the overall effect while adjusting stuff.