you need to add the vegetables and sausage to the slow cooker, season with marinara sauce, add seasoning, and mix everything thoroughly.
Then turn on the slow cooker and start cooking, you have two options: slow which takes 6-7 hours on low heat or faster which takes 3-4 hours on high heat, it’s up to you to decide how to do it, I would advise on low heat
When ready, take the sausages out and cut them into small pieces and put them back in the slow cooker.
After that you can eat it without garnish or with your choice of garnish,and don’t forget to add the parsley.