If you own the Bright Harvest content pack for Anno 1800 either through the Anno 1800 Season 2 Pass or by buying it separately, you will be able to access the new content in game. 
Tractor module and silo in farms
Should you be unable to access the new content, please make sure that the game is fully updated.
Bright Harvest info in main menu
When you load an existing save game, you will be prompted if you would like to import the new content. Confirm the import to access the new content in your current game session. 
Import prompt
In order to access all new content, your current city requires to have at least 500 Engineers (citizen tier VI). Once you fulfill this requirement, you will be able to build fuel stations from the building menu.
Fuel station in the Building menu
Tractor modules can be built from plant-based farms and silos can be built from animal-based farms.
Tractor module and silo in farms
Should you be unable to access the new content, please make sure that the game is fully updated.
You can find more information to Bright Harvest on the dedicated Anno Union post.
Feel free to get in touch if you have any further questions!