We're working to get more Windows Phone models supported worldwide. and when your phone is supported you'll be able to sign in with the same Microsoft account you used to join the Windows Insider Program. Windows Mobile Insider Preview currently works with the following phones—as long as they have at least 8 GB of storage, Windows Phone 8.1 was already installed on the phone at the time of purchase, and the version number is 8.10.14219.341 or earlier:
HTC One (M8) for Windows
Lumia 430
Lumia 435
Lumia 520
Lumia 521
Lumia 525
Lumia 526
Lumia 530
Lumia 532
Lumia 535
Lumia 540
Lumia 620
Lumia 625
Lumia 630
Lumia 635
Lumia 636
Lumia 638
Lumia 640
Lumia 640 XL
Lumia 720
Lumia 730
Lumia 735
Lumia 810
Lumia 820
Lumia 822
Lumia 830
Lumia 920
Source : Microsoft.com