Is it possible to add candidate directly to a position using the position record ID or do you add the position ID to the candidate record?

You need to specify both and use this endpoint:
POST /interviews/

I did the POST

While using it I used the body:
{
“CandidateId”: “606244564603103”,
“InterviewType”: {
“UserDefined1”: “14”
},
“JobId”: “EB-1068864940”
}

It still gives error:
{
“errors”: “InterviewType is Required.JobId is Required.”
}

also
is the position ID is different then of the job ID

I want the API to add candidates to the specified position

Interview type is Steve

step in the process is API.

This way I will know that the candidate has been added by the API process rather than a manual process etc

I have now created a user defined step for the API – user defined step 15

Is there a way for the API to request the job ID?

If you can suggest how best to get this all done

Yes, it’s asking for the JobId, not the PositionId. Also I believe you just want InterviewType = 14.