How can an HTC 8S Windows Phone 8.1 Update from Windows 8?

[Windows Central Question]

how can HTC 8S Windows Phone 8.1 Update from windows 8

i have HTC 8S Windows Phone 8 i need to Update into 8.1 how can i do it dos not update auto mode is is always show up to date plz sugest me some of line tolls for 8s