Here is the TANE manual.
https://steamcdn-a.akamaihd.net/steam/apps/24670/manuals/Trainz_Simulator_12_Manual.pdf?t=1447354291
The process is exactly the same as it was in TRS2006, TRS2009, TS2010, TS12, and TANE.
I highly recommend doing simple stuff first before getting into the complex session building with lots of triggers, scripted signal-links, path setups, EITs, etc. Once you get the basics down, venture on and learn more.
When developing a session, make a plan. I use Microsoft Excel to list out my track marks, stations, and industries including portals. For large routes, divide the route up into "divisions". Each division is a set of driver commands needed for that part of the route. This process night take a few tries to get it right, but it'll be the best route, no pun intended, to get things nailed down pretty quickly afterwards with very few mistakes.
Once you've got that done, create a session, other than default, and call it something useful so you remember what it is.
What really helps in the process is the Schedule Library. This is a script (built-in) that's added to the session. You then add in Copy Commands From... to the driver commands. This will help you setup the divisions. On my very large Ozark Valley and Western, which is an amalgamation and merger of many large routes including East Kentucky, Dave Snow's Ozark Valley, and other routes by Jointed Rail and others, I setup commands for each part. There's the East Kentucky Div., with its set of commands and track marks. Then there's the Ozark Valley proper, that's then followed by other divisions.
To use this, you click on the Schedule Library, instead of adding in the schedule to the drivers directly.
Create a schedule and name it, add in your commands, but don't include the repeat command here. You can create a bunch of schedules here and this is where this is very useful. Once you're done creating all your schedules, edit the drivers where you choose Copy Commands From... driver command. Click on that and choose insert and add from library where you choose your schedule. This is really helpful for setting up ports.
I also creating a bunch of ready-made consists with and without engines. This will come in handy for populating sidings, yards, and even industries where you can delete various train cars as needed to suit. This helps keep the kinds of cars consistent with the traffic you are running on your route. These ready-made consists go a long way for populating portals. Instead of adding one freight car at a time to the driver, you choose read-made consist. Insert that instead, edit to suit, meaning delete or add, change, freight cars if you want. Add your driver when done doing that, and above all, insert your Copy Commands-from command - choose from library of course. Done!
The biggest part, however, is planning and knowing where the track marks are. I spent a couple of days planning out routes on a very large route that ultimately was divided up into divisions. Once a consist was given commands from one division, I added in another copy-commands from command for another division. The only requirement here is to put in a wait command from about 20-seconds.
Anyway as I said, once you get the hang of the basics, you can then do the more complex triggers, mission codes with EITs, and other wiring part that takes a lot of complex work and lots of extra thinking, but with little experience attempting such an endeavor is not only overwhelming, but also frustrating.
