[Koha] 3.2.7 noZebra to 3.4 Zebra

I'm currently running 3.2.7 noZebra although Zebra packages have been installed. I'm going to 3.4 with Zebra. The question is: should I convert to Zebra before or after I do the upgrade to 3.4? I tried to switch to Zebra once before on 3.2.2 and couldn't get it to update properly when cataloging. Where is a good description of how to switch to Zebra? Thanks -- Bob