Two part process. OS 10.6.8 can not upgrade directly to Sierra (10.12). You have to upgrade to El Capitan (10.11) first. Then after that is complete you can upgrade to Sierra.
I already know about the need for El Capitan, hence my post.That's right. And the version of el capitan to use is the one which is still available on the mac app store at https://itunes.apple.com/app/os-x-el-capitan/id1147835434?mt=12
heres a link on a video how toI find the info on the Apple upgrade site confusing. Can I do this upgrade directly or is it a two-part process?