I recently resignated and am in the process of writing a resignation report, depicting resons for my resignation, don't know how to start it. Please help!

Do you mean 'resigned' as in quit. Then your resignation report should include all the reasons you resigned. Did you have trouble with fellow employees, supervisors, etc. That should go in your report.

Generally when one resigns, its simply done in a letter like:

To Whom It May Concern

Please accept my resignation from the company effective xx/xx/xx.

Nothing more than that is required. Some companies do conduct exit interviews to find out why you are leaving. Just tell them the truth.