You can play No Nonsense Hard Superflat by adding the server in the Minecraft launcher.
On Minecraft Bedrock Edition, open the Minecraft launcher or Minecraft app. Go to the “Servers” tab and press “Add Server.” Enter the No Nonsense Hard Superflat IP Address nonomc.comin the “Server Address” and the No Nonsense Hard Superflat port 19132 in the “Port.” Then press “Save” and start playing.