If you are creating a FSx file system, and want to connect it to AWS Managed Active Directory, then you will need to create a VPC Security Group with the following ports:

Inbound ports
Rules Ports
UDP 53, 88, 123, 389, 464
TCP 53, 88, 123, 389, 445, 464, 636, 3268, 3269, 9389, 49152-65535

Outbound ports

All traffic, 0.0.0.0/0