The *normal* rules are that you can change your tickets to any date this calendar year with no penalty, but if the price of the new dates are higher, you’ll pay the difference in price between what the tickets were worth when you bought them and what the current list price is of the new dates. You can do that in the app, by phone, or on the Disney World website.
If you choose not to go this year the tickets would expire and become basically a coupon off of the purchase of new tickets in the future, although using those “coupons” may require a trip to Orlando (Disney has stated they are trying to make them useable online but I haven’t seen anyone post that they’ve been successful so far). The “coupon” would be worth what the face value of the ticket was when you bought it (not the lower amount that you paid
UT).
That’s the normal rules however no one knows if Disney will add additional flexibility or not.