Create a Selector for an Existing Student Profile Category
Create a selector for the new Student Profile Category
Go to Email Settings > Selectors > Select Add

You must use the same naming convention as in the Student Profile Category (SPC)
Example: uses Student Profile Category Multi-Parent Arrangements

1 Description: must match the SPC
2 Variable Name: short form of description (no spaces or capital letters)
3 Type: 2 Options

4 Select the Student Profile Category (SPC) that was created above
Sample Email Template using Selectors
Below is an example where Preferred days have been setup as Student Profile Categories, then added as Selectors.
How to Add Preferred Days for Toddler and Kindergarten to Your Email Template