Before you begin sharing and telling others, the first thing that anyone can do to contribute is by signing up to make an account.
The most simple way anyone could contribute is just by spreading the word! Tell your neighbor about the cause, tell your friends and family about it, anyone interested in genealogy, their family history, or history in general! Tell anyone who might be interested. Or tell just about anyone, since WWII has had an effect on us in some way, whether through the modern political, social, cultural, and economic climate, or through your family who lived through it.