If you wish to include the schema for a YAML Schema file in an existing model, the process is slightly different.  With your model already opened, choose Tools > Reverse-Engineer > YAML Schema.  

The structure of a JSON Schema can be imported either as an entity in the Entity Relationship Diagram, or alternatively as a model definition so it could be re-used in the model:

If you wish to force the destination of the reverse-engineering operation, you may specify the container in which the entities should be inserted.

For RDBMS targets, an additional option appears, that allows automatic normalization of complex data types: