You may modify your offering at any time.
All you have to do is go to your offering page and edit the offering. Changes are saved automatically and published.

What aspects of the offering can be modified?

All configurable aspects for your offering may be modified even after the offering is created, whether it is published yet or not.

You may not remove data from your offering immediately for a transaction in progress with an acquirer. You may only remove data once the transaction is complete.