Adding SSL to a Fargate cluster

How can I add SSL to an application load balancer that services an elasticache and a fargate cluster? I have been studying this project for setting up a serverless graphql endpoint which has a proxy in front of it for monitoring and caching purposes.

The whole project works great but the endpoint itself does not have SSL enabled. If I manually add 443 handling to the ALB, it isn’t quite enough and it is due to the architecture that I don’t quite understand. The load balancer has a dummy target group that is empty, and I’m not really sure how the messages actually get to the servers from the load balancer, which has prohibited me from adding the SSL. This is what the stack looks like:

Does anyone have any advice on how to add SSL to this project?