Migrating On premise windows Domain controller to AWS EC2

There's a pretty good outline on all of this available here including the steps you'd need to take to promote your EC2 instance.

It really boils down to just these 2 options.

1. This assumes that there is network connectivity either Site-to-Site VPN or DirectConnect between your on-premises environment and AWS without overlapping CIDR ranges. For this, just stand up new EC2 instances and dc promo them as additional domain controllers in your forest. Once the new DCs are fully operational, you can set their IP into the DHCP option set for the VPC.

2. If you don't plan to connect the two environments, then you can use the AWS Application Migration Service or VM Import/Export to make block-level duplicates of the on-premise servers, even keeping the on-premise IP addresses (if the network topology allows it).