"The Windows Insider application provides registered Windows Insiders the ability to receive pre-release OS updates on their phone, directly from Microsoft. For more information about registering and becoming a Windows Insider visit http://insider.windows.com.
NOTICE: Windows 10 not already released and dont ask for date...
Tutorial how to sign up for upcoming preview (test) versions of Windows 10 for Windows Phone
1. go to http://insider.windows.com and select "Get Started".
2. login to Microsoft account (you must use your Microsoft account which you use on phone)
3. select "I accept the terms of this agreement (required)" and "Submit"
and that all
4. install Windows Insider application to WP8 phone http://windowsphone.com/s?appId=ed2b1421-6414-4544-bd8d-06d58ee402a5
5. run application and select "Get preview builds"
6. select "Microsoft account" and login with your account
7. and that's all for now. Is no Windows 10 builds in moment... it's expected to come in February
NOTICE: Windows 10 not already released and dont ask for date...
Tutorial how to sign up for upcoming preview (test) versions of Windows 10 for Windows Phone
1. go to http://insider.windows.com and select "Get Started".
2. login to Microsoft account (you must use your Microsoft account which you use on phone)
3. select "I accept the terms of this agreement (required)" and "Submit"
and that all
4. install Windows Insider application to WP8 phone http://windowsphone.com/s?appId=ed2b1421-6414-4544-bd8d-06d58ee402a5
5. run application and select "Get preview builds"
6. select "Microsoft account" and login with your account
7. and that's all for now. Is no Windows 10 builds in moment... it's expected to come in February