How do I insert a new related record with the API?

How do I insert a new related record with the API?

Hi there.

On the API I see methods for getRelatedRecords and updateRelatedRecords but I'm after inserting a related record.

To be specific, I'd like to programatically create a list of related Products for each Potential. Is there such thing as insertRelatedRecord?

Is this possible with the API? 

Thanks