Clarifying and breaking big goal into smaller sub-goals

How can I clarify my next steps of a huge project? My goal is to pare down my paper collections by 2/3s. Clarifying and breaking the big goal into smaller sub-goals and next steps. I want to finish up of paper files. I am lacking determination with that. I think that’s because I have not been able to clarify what is next. I do have difficulty both in finishing and in starting projects.