How we can create and debug a remote event receiver and attach it to existing list

I have a custom list inside our SharePoint online,and it contain many items. now i want to add some business logic to the list through implementing a remote event receiver which get fired when items are been created and edited. but i am not sure how i can attach a remote event receiver to existing list? last time i did so was around 3 years ago, where i follow the steps mentioned on this link and they worked well for me @ Attaching Remote Event Receivers to Lists in the Host Web . but recently when i tried this appraoch, i got an error related to the fact that azure service bus (which will be used to debug the RER) has been retired and can not used any more to debug remote event receivers. now i found this link Remote Event Receivers Creating and Debugging in SharePoint Online, but it does not show how to attach the remote event receiver to existing list, as in this link they added a new list as part of the remote event receiver project… so can anyone help me in finding a full documentation on how we can create and debug a remote event receiver and attach it to existing list in sharepoint online? Thanks