Once you have upgraded to the DC UNIVERSE INFINITE Ultra tier, your benefits begin immediately.
If you upgrade between paid plans, you may be eligible for a partial refund for the time remaining on your existing subscription, pro-rated based on the price difference between plans. Subscription fees are otherwise non-refundable. After your subscription expires, it will automatically renew at the then-current rate (plus applicable tax) on a recurring basis, unless you cancel before the renewal. Any benefits, savings or promotional periods specific to your original subscription will not apply after your plan automatically renews.
See here for all that the DC UNIVERSE INFINITE Ultra tier has to offer.