-howto add a good:

go into the goods folder and create a new file, the filename does not matter. The filestructure looks like:
with GOOD_NAME beeing the name of the good an GOOD_PAYS the price per ton.

-howto add a trainengine:

go into the modelsfolder and copy your model(s) there, should be 3 for the 3 lod's. go into the objectsfolder and create a file. The filestructure looks like:
objectname a3-1
model13ds a3-1.3ds
model23ds a3-2.3ds
model33ds a3-3.3ds
gifimage testlok.gif
axevorn 3
axehinten 2
length 18
type engine
maxspeed 120
ps 2000
model1-33ds are the models, gifimage points to the image that is used in the depotview, axevorn and axehinten indicate how far the wheels are behind the start/end of the model. Length is the length of the model (1 in the 3d editor=20 in zugspiel) maxspeed and ps have no effect atm.

-howto add a industry:

The filestructure looks like:
objectname farm
model1 farm.tri
model2 farm.tri
model3 farm.tri
type industrie
sizex 4
sizey 4
produce livestock
productionamount 30
produce grain
productionamount 25
requires coal
requiresamount 20

-howto add a carriage:

The filestructure looks like:
objectname oilwagon model1 oilwagon.tri
model2 oilwagon.tri
model3 oilwagon.tri
model1full oilwagon.tri
model2full oilwagon.tri
model3full oilwagon.tri
gifimage oilwagon.gif
type wagon
axevorn 0
axehinten 0
length 12
loads oil
capacity 20
this one loads oil and 20 units of it max. modelXfull means model to use when the carriage is full.