When does this process begin? Is it set or can leagues do it whenever they want? I saw one old post that references start date of 10/15 and runs through 11/15, but post is very old. And how exactly will the process reveal itself to the league to complete?
Here’s a post from Niv from a couple of days ago that specifies that arbitration will begin on 10/15/21.
I’m not sure that I understand the last question. IIRC, there will be a link on the league homepage and a banner posted to remind people to complete it. Most commissioners also will post reminders on the league message board and/or email individuals who haven’t participated.
Click the little “tools” icon up near the top of every page which defines important dates.