Is it any wonder when you simply cannot be bothered to read the manual? Next you'll be asking how to create paths on routes so you can start wherever you like...
Off the top of my head - don't blame me if I forgot to add a bit.
Creating Consists
1. Load 'Editors and Tools'
2.Click on 'Activity Editor'
3. At the top left, click 'File' and then 'New' and select any route from the menu that pops-up, same with the 'Activity Name' pop-up. Neither of these matter.
4. In the right column click the 'New' button that is under the heading 'Player'.
5. In the window that pops-up, click the 'New' button under the heading 'Consist'.
6. Then type in the 'Name' and 'Display Name' fields something that will make you remember what is in the consist. I usually use the same name for each e.g. 2SPTClass334s shows it is two Class 334s in SPT livery joined together.
7. Double click on the stock you want in the consist. You must only choose ones with the small symbol on the left for the driving vehicle as it denotes they have a cabview. Ensure your stock has the same brake type. Train Sim will only stop you having trains joined together if they have different couplers. If you wish to remove an item from your consist, drag it from the preview pane to the small square icon above the preview pane.
8. When done, Click 'Save and Exit'. Then close everything else down.
A Path creation tutorial can be found on my website -
http://www.virtual-rail.co.uk/mstspaths.htm