Using Simple Control outside your home network to control your home devices requires designating a hub on a dedicated iOS/tvOS device, or in the background on a macOS system, which is supported on macOS, Apple TV, or iOS (part of Simple Control). Activate the “Allow Remote Access” option by going to Menu > Settings > Simple Hub in Simple Control. Simple Control must be paired with a device designated as a hub and logged in to a Simple Control account.
Simple Control is able to automatically create a remote connection. To do so you will want to be sure that your router is enabled to support UPnP and/or NAT-PMP.
If you are not able to automatically create the connection using Simple Control, then you can create the port forwarding in your router’s settings for 47148 and in the Simple Hub settings screen enter in your External IP or DDNS in the hostname field.
The Setup Guide goes into further detail on designating a hub and remote access.