The 90 day support is for any and all Windows 8 related support issues, not just installation/activation issues, to my understanding. Go to and click on "Get live help" in the sub-header, then click on "Windows 8" just to the right. If you look on the live support page under the Windows 8 menu, there is a wide range of issues one may click on. (These are all live links, by the way):

Windows 8

Select a topic

And most of those have sub-menus that slide out of the right side of the page.

But to get a live chat with a Microsoft Support Tech you will have to visit the support page, as described above. I had a very good experience with Juan V. I had a bad burn on my DVD, and the failed install left temp files and some files in the Windows folder that were fouling up the install with a correctly burned DVD