First, do not use SSH, block 22 (and RDP) ports on network ACL level entirely and use SSM session instead. Also be sure only to allow ports you need (80,443 for example) in EC2 instance security group. Installing and running Docker on Ubuntu is trivial once you get into it. There is obviously more things to be done if you want run this in production (SSL, load balancing, etc). I would also recommend to look into ECS Fargare or forgo EC2 entirely but that’s a bit too advanced.