First, ensure a survey has been created via Products>Policy>SurveyCreation with the Create as attached survey checkbox ticked.
For new policies: open your policy via Products>Policy>Policy Creation>Create For existing policies: open your policy via Products>Policy>Policies in Progress>Actions column >Options>View Policy.
Under the Options tab, set Attach Survey to Yes.
Under the Options tab, search for the survey created in Step 1 in the Attach the following survey box.
The policy can then be saved or published with the survey attached.