Yes, you will need to define a process for the trigger to launch. Below I have connected the Trigger to the simple sample process "Hello World"
In a real world case this process would do different things depending on your needs. If you have a single action that all emails should cause to happen then you could create a process that the Trigger launches which carries on and completes the entire business need; if you have different emails that should have different processing paths, the Trigger process should retrieve basic information from the email and launch the appropriate process based on the emails contents.