Here is a video which explains how to make videos automatically play as a trailer on your YouTube channel. Below the video I give you the step by step guide with photos. Hope this makes your life easier.
1. Log into your YouTube account.
2. Click on “My Channel ” Link On Your Left.
3. Click on the edit icon to your right then click on “Edit Channel Navigation” in the dropdown.
4. Click enable “Browse” in the next window.
5. Click select channel trailer.
6. Click on the video you want to have playing automatically when people visit your YouTube channel.
7. Click save and your done.
I then suggest logging out of your YouTube account and going to your channel page. You then should see that your selected YouTube video plays automatically when people visit your channel. You might want to put a video that tells people something about your channel in this position. Up to you.
When you make comments on videos and people click on your username to check you out they will come to this page.
Hope this helps! If you found this useful please like and share. Thanks! Matt.