You will need XACARS available here:
http://xacars.net/
Just download the X-Plane version, unzip and place it into your resources\plugins folder (in X-Plane, everything is installed by unzipping and placing in the subfolders).
I also can highly recommend to get the Zibo Mod for the default Boeing 737-800, and the corresponding Audiobird soundpack. All is available for free, but it adds greatly to the immersion when flying the B738. Download and instructions here:
https://forums.x-plane.org/index.php?/f ... oad-links/
If you're flying in the US, I can also recommend having a look at Forkboy's Ortho overlays:
https://forums.x-plane.org/index.php?/f ... thophotos/ - they're visually great, and represent the terrain quite well, including cities, road networks, buildings, ... and all that for free.
Generally I recommend familiarizing with
x-plane.org, a big community providing help and support, and tons of free downloads (aircraft models, scenery, libraries, plugins, ...)
Once accomplished, you can start having a look at payware. For X-Plane, there are quite a few good airliners out there, but they're mostly payware. Most notably:
- ToLiSs A319
- Flight Factor A320
- IXEG Boeing 737-300
- Flight Factor Boeing 757
I just listed models being fully compatible with X-Plane 11 and being represented in the ACH fleet.