After setting up your form fields, making sure that you already have either a Dropdown, Multiple Choice or Checkbox field to use as reference in setting up where submission notification goes depending on selected options, you can proceed with setting up the form rules.
To set form rules, go under "Logic" under your form, and then select "Form Rules" on the left.
Select "Create a form rule", and then select the option to 'Send Email".
It will then give you an option to add a notification email.
From there, be sure the email address is saved by clicking on the small, circular plus (+) button beside it, otherwise there will be no destination for the form to be submitted to using the form rules.
Click on the big, green plus (+) button on the first rule you made to create a copy of it. Configure the new copies to correspond to the other options. Below is an example of how different options are set for different email notification recipients.
Make sure to click the "Save All Rules" button when you're done and choose to preview your form in order to test things.
We also have a general tutorial on Form Rules here.