As the employer it is your role and legal duty to ensure the health of your workforce in relation to any risk of or from exposure they encounter at work. A competent occupational health service provider will be able to help you prioritise and make decisions.
You should;
Share your risk assessments with your occupational health provider
Make sure they observe the workers and the work they do by giving them time to do this
Come up with a list together under red ( must dos) , amber ( good practice) and green ( e.g. lifestyle issues not legally required or necessarily work related)
Set up front your expectations from the service being provided
Communication
Feedback of results
Roles and responsibilities
Agree a timescale for review.