Spout from OBS Studio is very useful for video inputs into Unreal Engine because Unreal doesn't recognise a lot of capture cards/ video formats:

1. Ensure that your Spout input from either from OBS Studio or another compatible program is set up and active.
2. Add a new 'Spout Receiver Manager' Actor and in the 'Details' panel select your Spout input from the drop-down and create a Render Target to receive it:
3. Set up your Composure comp following the instructions here or a video guide.
4. Select the 'Media Plate' from your comp in 'World Outliner', go to it's 'Details' panel, add a new 'Input' using the 'Array element' and select 'Texture Input':
5. In the 'Texture Input' drop-down, select the Render Target you added in step 3 above from the 'Search Assets' list:
6. You will now be live-streaming your video input from Spout or OBS Studio into Composure!