How to attach attachment in Unifier Workflow BP record using Rest Services in Update function

Hi All,

We are trying to attach document in Unifier using Rest Services to a Workflow BP. We have a dedicated Rest Services to create a BP record and add attachment to it.

However we don't have any Rest Services to add attachment, update the BP form and move the workflow to next step for a line item type BP. Could you please help us with the proper instruction how can we add attachment and update the BP using Rest Services.

Thank you