I actually wrote this up in a few blog post here[/url] and here[/url].

The link provided in the previous post is the link that takes you to the latest release of SSDT, but you can go down to this section in on that page, it will take you to the VS 2013 download for SSDT and SSDT-BI. At this time there is no SSDT-BI released for VS 2015, you will have to stick with VS 2013 or at least I would suggest that version instead of VS 2012.