Workflows with Merge forms

To put it simply, I've never worked on a workflow using merge forms. I've set the start condition to merge forms but nothing is appearing in the drop down lists. Does anybody have some documentation links they can share or some tips?

Thanks.

Hi Rhys, 

did you select the fillable PDF?

Greetings from Germany,
Simon H. Hellmann
DocuWare System Consultant

I hadn't, but now I have and it works. Thanks