Rhetorical Devices are meaningful labels assigned to spans of text, usually one or more phrases. To assign one, the starting line has to be made known to the system: You do this by calling up the Attribution floater, which has many uses. In the TLS, these are a special case of observations that can be recorded; see Recording observations for some general information about how to use the dialog to define the end point of the text span of interest.
Here we look at the specifics of Rhetorical Devices. When assigning them, it is essential to connect the location in the text to the definition of the Rhetorical Device. This is done by starting to type the name (or even a part of the name) into the input field labeled ‘Name of Rhetorical Device’. The whole process from opening the dialog with the ‘speech bubble’ icon to saving to the database can be seen in this screen cast:
And this is the resulting annotation, showing only Rhetoric and hiding the Grammar for clarity:

As can be seen, the first and last line have the annotation ‘ENUMERATIO’, where the yellow bullet stands for Rhetorical Devices and the direction and position of the parenthesis indicates the first and last line — this becomes important when there are multiple intersecting annotations.
If the name for the desired Rhetorical Device does not exist, you can still press save and will now be shown an alert where you can confirm that you will be creating a new entry, and given the opportunity to modify the name — like the pre-existing names, an all caps name is desirable. This will then open the Creating Rhetorical Devices dialog.