Once defined (here), entities may be used in profiles. Entity data is stored in a profile's Parametric Fields (here) via Data from Field rules (here).
The easiest way to use entities is by adding them at profile creation (here): entities are simply chosen from the available list. Appropriate Parametric Fields and Data from Field rules are then automatically created.
To use entities on an existing profile, ensure appropriate Parametric
Fields exist for the desired entities, using Tools →
Parametric Field Tools if necessary. Since an entity may be
found multiple times in a document, a Set
type field is usually
appropriate. Then create Data from Field rules to copy each
entity to a desired Parametric Field: choose the desired entity in
From Field, and the target Parametric Field in To Field.