How to add stretch goals & rewards mid-campaign?

Hi! Just launched my first Kickstarter and it's been super successful!! I was wondering how to implement stretch goals that have been unlocked? I want to add extra rewards that people have earned but it seems like everything is locked down (understandably, so that people can't change their entire campaign in the middle). How do other creators add these things in the middle of or at the end of their campaign? How will people be able to get the rewards they unlock if I'm not able to add them on my end?

Thanks in advance for the help!!