how to map an existing custom domain name with ALB to run a containerized application?

I have a custom domain name already created in my account in aws. I would like to map this to an application which i will be migrating to aws . I have not worked with the aws ecs, alb services yet, but i assume they should be able to configure easily. I have created an application and containerized it. once i push this to say , aws ecr, what is the workflow to create all the things i need to run my application in aws. i have the domain name, do i need to create an ecs cluster first, or alb first? is security group that allows traffic on port 80/443 enough, if i want to run the application in the vpc and how do i map my domain name to this application running within vpc is there an example of this , or cloudformation templates that would be helpful to get started?