Where can I get ISTA?

Title really says it all. I’m sick of going to the dealer and being ripped off, and I also like working on my car so I figured I’d give a few more complicated but not beyond my scope repairs a try. Where can I get ISTA, though?

Does BMW TIS come with ISTA? Does having the newest version matter?

I have a 2013 535i xdrive if that helps in any way.

Thanks in advance!