If the reward tier or add-on you’re looking to edit already has backers associated with it, you won't be able to make any changes to it (except for specifying new countries that you'd like to offer shipping to, or to increase the quantity).
However, if a reward tier or add-on doesn't have any backers yet, you're welcome to make changes or delete it entirely. Select “Edit project” from the creator tools menu, located on the left side of your project page, to edit your rewards.
Can I change the estimated delivery date of my rewards?
Similarly, if no backers have selected the reward tier or add-on, you can change the estimated delivery date. If the reward has already been selected the date cannot be changed, so we recommend notifying those backers of the new estimated delivery date.
Take a look at our “Can a project be edited after launching?” for more information on the changes you can and can’t make while your project is still live.