I am a new user, just bought a subscription with two assessment tests.
It's unclear to me how to use them. It seems to tell me I have to activate within 14 days. But if I have two years on the subscription, why would I active both tests now?
Can someone explain to me how to use these? I was thinking of activating one a month down the road (midway through my summer semester) and then take another in six months.
Again, any help on this is appreciated.

You do not need to use them now. Once you activate them, you have 14 days to complete it and then your results are available to review for a short period of time. I have the same subscription and used one at the beginning of studying and just used the other one.