Partnersource:
https://mbs.microsoft.com/partnersource/global/support/support-news/msdnav2015download
P.S.
Microsoft Dynamics NAV 2015 Readiness Library
https://mbs.microsoft.com/partnersource/global/readiness-training/readiness-training-news/NAV2015ReadinessLibrary
Get Ready for Microsoft Dynamics NAV (2015)
https://mbs.microsoft.com/partnersource/global/readiness-training/readiness-training-news/GetReadyforMicrosoftDynamicsNAV