Start by clicking the Automations side navigation options and then clicking on Properties to find a table with all of your properties.
Once here, you can click Add Property and a pop up will display allowing you to name the Property Definition
You must select whether this Property Definition will be assigned to Crowds or Members, and then simply click Save.
Crowd vs. Member?
Not sure which type your property definition should be assigned to? Below are a couple of examples to help you decide.
Crowd Examples:
Department (ex - Front of House, Sales)
Store (ex - Main St Location, Broadway Store)
Member Examples:
Hire Date (ex - 01/02/2005)
Job Title (ex - manager, bartender)