Help in application to be accepted for a Phd

I have no idea where to start, there is just so much information I feel is needed but I just don't know where to start. How does someone who is 57 next birthday write an application letter to convince academics to take her on to do a Phd?

Yes, most likely self funded, but wouldn't it be nice if someone else had the faith that you can do it and generously award funding just towards the fees. That apart, 57 is a ripe age, I have done so much. I have three nursing qualifications and reach the top grade in nursing twice. Once before my three children were born and again when I returned to nursing when the children were older. I started my first successful BSc when the children were little, then studied full-time a BSc (Hons) later. Then I had a brain infection and could no longer nurse. Cried for five years then pulled myself together and successfully received a Master of Research. This was in an area of research I had never studied before and was intended as a way of proving my brain works!

I was retired through ill health ten years ago and I am just bored stiff doing casual reading and fun things, I want major challenges. I just can not let go. I'm guessing because I have reached the top in everything I have ever done this is what is causing this nagging NEED for me to carry out a Phd.

So how, please, to do sell myself as a suitable candidate to work towards a Phd, and hopefully benefit others in me doing so??

Thanks for any guidance you can give (even if it comes down to just don't even bother, at 57 no chance!!)...Carte