For an explanation of Custom Fields, see What are Custom Fields?
STEP 1: BROWSE then click on CUSTOM FIELDS.
STEP 2: Click ADD CUSTOM FIELD .
STEP 3: SELECT OBJECT: (drop down) choose where you would like to add a custom field to.
(c) Owner: (pertains to content of a sub-account for Metrixstream Professional Plus or Enterprise Editions)
STEP 4: Enter a field name: (internal only) A name you would like to reference to. E.g. age, hair color, etc...A way to reference data
STEP 5: CHOOSE FIELD TYPE: E.g. you would use INTEGER if you were only to have age (number).
STEP 6: ENTER DEFAULT VALUE: (strictly optional) Normally this would be blank, but you have the option to specify a default value, if it makes sense for your application. E.g. You want new content owners to always receive email updates by default.