Hello Harold. I suggest you hold off a bit, as we are currently experiencing difficulties with the multiplayer and download station servers.
Before we get started, make sure Trainz.exe and all the .exe components in ts12/bin are set to run as administrator. You can find several guides here and elsewhere on the Internet for getting that done, in whatever version of Windows you may have. You may also want to take complete ownership of C:\Program Files\N3VGames (for 64-bit OS, C:\Program Files (x86)\N3VGames). Then, apply the necessary patches to bring your build version up to 49922. You can find your build version in the bottom-right corner of the launcher. Note that some copies of Trainz, such as those purchased from Steam, can not be patched thanks to Steam's EULA.
To get new content, launch Trainz and click "Content". You may see a popup within Content Manager 3.6. Ensure your PlanetAuran login details are entered correctly in that popup, and hit Save. You can search for multiplayer routes and sessions using the intuitive searchbox. I recommend the Port Ogden and Northern TS12 MP route and session by colourlight as a start. Be sure to download all route and session dependencies, including sub-dependencies. You can see which assets are missing dependencies by clicking the "Missing Dependencies" tab. If you do not have a First Class Ticket, you may find download speeds to be slow, and you won't be able to download more than 100 MB per day. You can purchase a First Class Ticket from the Auran Shop. Most Trainz DLC and base-game purchases from the Auran Shop include a voucher for a discount on a First Class Ticket.
If you have any further questions, don't hesitate to reply to this thread. Myself or another community member will be happy to assist you.