I take it you mean automated trade routes?
You need to go into the city screen, and to the right of where it lists what is being built in the city, there should be three buttons, the Map, the Production Queue, and the Imports/Exports. Select the Imports/Exports, and a new menu should appear.
If you want your city to Export Silver to Europe, you need to select the Exports button, and then a menu will pop up where you can control how much is exported, etc. If you want to import Tools from Europe, you need to select Imports and do something similar.
Then, you need to exit the city screen, and select a transport (a ship), and click the automate trade routes button, and a menu will pop up with a list of all the things you have set in the city screen, and you need to click on the export/import that you just set in the city screen.
If you just do one of these things, nothing will happen- you must make a city export or import something (and define where it is exporting/importing it from), and make a transport use that trade route.