You are downloading the Star Walk XAP file v220.127.116.11 for Windows Phone. Star Walk is a paid Education App: Star Walk is the most beautiful stargazing app you’ve ever seen on a mobile device. It will become your go-to interactive star chart of the night sky,. You can now download the offline XAP package file to install & try it.
Download Locations for Star Walk 18.104.22.168 XAP file
To try to install it manually from an SD card, you should choose one of the server location above to get the offline Star Walk XAP file, move the file to your phone's SD card and then tap 'Install local apps' in the phone's App list.