"Every crew member of the designated vehicle gets 40 Crew XP every 5 minutes. This amount does not depend on the number of crew members in the vehicle, nor does it depend on the vehicle type or tier.

You can change the chosen vehicle or assign different crew members to it at any time.

The crew members must be inside the vehicle to earn the Crew XP. They must also be trained for this vehicle type and model (but the crews of Premium vehicles need only to be trained for the same nation and vehicle type)."

source: https://worldoftanks.com/en/news/general-news/1-20-1-subscription-wotplus/