Lightweight Gateway
If port mirroring data to the ATA Gateway sounds too complicated or too involved for you, make sure to check out the new ATA Lightweight Gateway. This is an ATA Gateway component that installs directly onto your domain controllers, so you don't have to make changes to your networking equipment. While this is a much easier approach to getting the data from your DCs into ATA, it does come with some drawbacks that I wanted to take a minute and point out.
If your environment flows more than 10,000 packets per second from the domain controllers, then you should run a real ATA Gateway, with the port mirroring setup. Typical domain controllers will be well under this number, but in large environments it will be a consideration. There is a sizing tool available on the ATA website which runs in your environment and captures these numbers on your DCs. You can download that here: https://aka.ms/atasizingtool.
If your intended purpose in having ATA is to be SUPER secure, then you should...