Once you have Editorial installed, a new item in the share list in Working Copy will appear - Edit in Editorial. Using that will prompt to install an Editorial workflow. Official instructions are here.
I occasionally get errors about an incorrect URL callback key. I believe what this means is that the sync marker (a suffix on the filename, like #12345) is missing, perhaps due to using 'Copy to Editorial' instead of 'Edit in Editorial'. Starting over from Working Copy seems to fix it.
Remember, in this flow Working Copy drives so start from there.
There are a few other tools I looked into, but decided against. Any one of these would probably be a great option if Editorial doesn't strike your fancy.