Hi,
This is Ashish with experience into Business Analysis. I have worked in multiple projects during my tenure which responsibilities like writing Business plans, providing Business solutions and defining functionality of the project.
You can start with the Statement of Work document which will helping in identifying the Problem scope. Then we can proceed with writing the Solution design document, when the proposed solution is accepted then we can go ahead with gathering the requirements. Looking at the description the project information is not much so I cannot specify much in greater details.
Looking forward to know more about your so that we can discuss the proposed solution and the documentation.
Regards
Ashish