File, save before doing anything else.
Then File, export, Trainz export XML. If Trainz export XML is not an available option exit Blender and ensure that the Trainz exporter has been installed in the correct script folder. You will also need to ensure it is available in User preferences under import/export.
Click OK to export the mesh data. Technically you can also export an animation here or scale the export if you prefer to work in feet.
In this case the file being exported is called Leopold street, it will create both the "leopold street.xml" file and a "Leopold street.im" file. File names without spaces in them are easier to handle so you can change the suggested file name to body to create a body.im file which is simpler in the config.txt file.
The export is complete.
Now to get the asset into Trainz we need some red tape so
Download kuid:86627:1791 this is the cylinder scenery asset. Clone this asset. Then use edit, edit in explorer.
Then you copy the .im, the "terrace one.tga" and "terrace one.texture.txt" file into the cloned folder. Now we have to tell Trainz to look at the new .im file so open the config.txt file in notepad and change the following lines
name "cylinder scenery" trainz-build 1.5 asset-filename "cylinder" username "cylinder scenery"
name "test house" trainz-build 2.7 asset-filename "body" username "test house"
Save the config.txt file and commit <Ctrl>M.
Now look for "test house" in surveyor.
Before uploading it you will need to do a screenshot and resize it to 240 by 180 .jpg, either rename this reskin240.jpg or change the name in the config.txt file. You will also need to go through the config.txt file and put your name in as the author etc.