Hi Christine,
Simutrans has a steep learning curve!
Freight can only be transported between two factories that have a contract. Vehicles won't load freight unless they know which customer wants that freight.
To see whether factories have a contract:
1. Click on a factory to open the factory window. Click in the grey box at the top to change the name. As an example, we'll call this one "the Original Vegetable farm".
2. Look under 'Suppliers' or 'Consumers'. These are the factories that have contracts with the Original Factory.
3. If you click on the triangles to the left of the Suppliers and Consumers, the game will show you their locations. Click on them and you will open their factory windows. You can see that the Original Factory is listed amongst
their suppliers or consumers.
4. You need to build cargo depots (or ports, airports, etc.) near both factories in the contract and then take freight from one to the other.
Depending on the size of the map, it may take the game a few minutes to calculate that you have linked the two factories and start them producing freight.
(Apologies, I have not had time to finish this post, but hopefully it is still a little useful)
