Dear Mr. Md. Iqbal,
In my view, you may do some of the tasks mentioned under as per your role in the project:
1) Start building team consisting of IT and functional persons. Functional persons must be champion in their area. these team members should be full time dedicated to the project-take commitment from higher management on this.
2) Inform the functional team to start preparing their processes with flow charts.
3) Get demo of SAP running at other production unit so that your functional team members can start thinking of mapping their processes in SAP.
4) Start learning ABAP if you are going to be ABAPer OR start understanding business processes slowly and gradually. Material management (purchase, warehouse) would be most important part to start with. You may get into other processes as per your area of interest and background.
Most IMP : find out project owner and project manager at your location for this project.
Documentation may seem boring but it will help in longer run so if possible, try to document each and every task, meeting, requirement, commitments from implementation partner, etc. Signing on the document is equally important.
If you are going to be project manager or similar to that, ERP Demystified by Alex, SAP Project Management by Joy Ghosh and many other books may help you further.
God bless you and your company grand success in the SAP implementation project.