@Alexa9006 As far as I know, you can only dedicate chapters to people on the website. Maybe there are ways to do it on the app, but I don't use the app that much so I don't know.
Assuming you use the app and you go on the website, all you have to do is sign in and go to ''my works'' by clicking the gear button under your profile.
Then, you choose one of your published chapters and go to the right hand side of the screen where either a thing with three dots is, or a word that says edit, I can't remember. You click on that and it says something about dedications for that chapter.