https://support.activision.com/articles/en_US/FAQ/Clan-Challenges-FAQ#q1
You can click that link for info from elite but I'll sum this up below
There will be weekly and daily challenges and both premium and non premium members can contribute!
There are 3 levels of challenge you can get, sort of like ops with Bronze, Silver & Gold.
This is more of a reason than ever to check the forum often, I'll get a new section up for challenges and try to check elite multiple times daily to catch all the challenges, I'll post a topic as soon as I enlist for one.
Currently it is blank, but I will keep my eyes open and enlist as soon as one appears!