To connect trådfri outlet to gateway without steering device:
1.Reset your trådfri outlet
Plug it in close proximity to your gateway (Mine was within 20cm). It should turn on with a visible LED indicator.
Use a paperclip or similar to hold down the reset switch that is close to the LED indicator
LED should start pulsing and you'll hear a click of the relay, remove the paperclip and wait for 5s or so, outlet is now ready to pair with Gateway or other steering device.
2. Link the outlet to the gateway
Hold down the pairing button on your gateway for 10s or so, found under the main lid, indicated by a chain-link icon. Don't confuse it with the reset switch.
You should see the LED on the outlet pulse differently and then stop pulsing.
Launch the app, you should get a notification saying 'control outlet found', with a 'rename' and 'OK' option. The app has acknowledged the existence of the new outlet, but will not allow you to control it yet. You might need to open settings first to see the notification.
3. Get the outlet to work in the app
Go to settings in the app. Beneath the rooms/groups you should now see a group called 'disconnected devices', your new outlet should be listed under it. It can be dragged from here to any existing room/group.
The app may ask you to press the link button on any existing steering device in that group - I'm not sure this is necessary as it seems to work without.
Go back to the main area of the app you should be able to find the new outlet and control it individually or as part of a larger group. I got mine to operate our Christmas tree lights as part of the main living room lighting.