Please guide

I own a flat which was transfered to me, by my parents (mother and father) jointly via a gift deed.

I am unmarried and dont keep in good health. to be on a safer side, I want to write a will, so that in event of my death my, this property should go 100% only to my mother and not to my father.

How do i proceed for the same. and what are the documetation and formats.

Please guide