How do I add contacts to the favorites list in the dial icon?

To add contacts to favourites open the phone app>favourites>click the plus icon on the top>select contact > choose an option> choose which app (for example if you choose WhatsApp and you choose phone I think that means a phone call on WhatsApp) Hope this helps!

I'm not sure what you mean by the "dial icon?" But you add people to your favorites in the Contacts App.

Read this --> Use contacts from the Phone app on iPhone - Apple Support

If this isn't what you're looking for, asking anyone here to fix anything won't help you. This is a user to user only from, which Apple doesn't participate, nor read for user feedback. You can provide feedback to Apple here --> Feedback - iPhone - Apple