Just found out that you can now upgrade without having to join the insider program and figured I share it.
AT&T forum with instructions
As the link shows it will update to Windows 10 version 10.0.10586.107 but I found out that you need to check phone updates again to get Windows 10 version 10.0.10586.318
AT&T forum with instructions
As the link shows it will update to Windows 10 version 10.0.10586.107 but I found out that you need to check phone updates again to get Windows 10 version 10.0.10586.318