A Send Emails option is available in the Options section, at the top of a selection rule’s toolbox:

If clicked when the current selection rule contains unsaved changes, or is invalid, a warning message is displayed.
Clicking the button at a valid, saved selection rule displays the Send Emails training aid, in which the following interfaces are shown in sequence:
•Ready to send some emails?
•Choose an existing Email
•Configure your Interaction
•Running your Interaction
•Interaction Created