Welcome to the world of Trainz, when you get into this sim it will take up lots of your spare time.
To start of load a map of your choice, you will then be in Surveyor where you can place trainz on the map and give your driver some orders.
First click on the rollingstock tab (the one that looks like a wheel on the right of the screen), scroll down and select a locomotive, click on the loco, click on the plus icon + then click on the track. The loco selected should now appear on the track and have a driver allocated. From here you can do a few different things, i.e. give the driver orders to drive to somewhere etc. or you can go into quick drive and drive the loco yourself. If you want to give the driver orders to go somewhere it will pay to have a sheet of paper and pen handy. Follow the track in surveyor and note down any track marks, industries or stations you want the driver to go via or go to. Once you know where you want to go click on main menu, edit session then driver setup. Your driver will appear at the bottom of the screen with a small green arrow icon just to the right of the driver's picture. Click on the small arrow icon and a list of commands will popup, click on a command and it will appear in the driver command bar at the bottom of the screen. When your list of commands is complete click on quick drive and the driver will carry out your commands.
Hope this helps,
If you are going to try cross-country skiing,
Start with a small country.