While the project is live
To change your reward selection while the project is still live:
On a web browser: Visit the project page and click the “Manage your pledge” button that appears next to your pledge amount. On the next page, select "Change your pledge", and then select the reward tier that you wish to change to. Next, you'll be able to add any available add-ons to your pledge. If you are pledging without a reward, simply update your pledge amount. Remember, it's only possible to select one reward tier at a time.
On the Kickstarter app: Go to your Profile, and click on the project under your Backed projects. Tap the Manage button, then tap the three dots on the upper righthand corner of the screen. This will open a menu of options—to change your reward or select add-ons, tap Edit reward. You'll first see your selected Reward and can change it if you like, then once that is confirmed you'll see available add-ons to add to your pledge.
After the project has ended
Please note that a pledge can only be updated while the project's funding period is live. If the project has already ended, you will not be able to modify your pledge amount or reward selection. If you need to seek out an alternative arrangement, please reach out to the creator directly.
To message a creator, visit the project page and click on the creator's profile name. This will open up their bio page where you can then click the blue "Contact me" button to send them a message via Kickstarter.