Update README.md

README.md

@@ -20,6 +20,9 @@ Set the following volumes with the -p tag.
 
 ## Example run-command
 
+Either use the docker image `tiynger/pythonflask` or run `docker build . -t pythonflask` in the top directory of this repository.
+If so you need to change the command below apropiately (`tiynger/pythonflask` to `pythonflask`).
+
 ` docker run --name flask -v flask:/flask --restart unless-stopped -d -p 80:5000 tiynger/pythonflask `
 
 ## Included Python3 packages