“... I edited the /boot/config.txt file.
My first experience was that I just got a blank screen and no signal. I came to look at the reviews to see if anyone else had had a similar experience but no one had. Therefore, having found the solution, I think it may be helpful for anyone else in the same situation to know I had to set:
in /boot/config.txt, which can be edited by mounting the SD card on another computer. The exact options may vary for different monitors - see http://elinux.org/RPiconfig#Video
Now it works correctly and I am very happy with it.”