HowTo: redirect my.domain.co.uk to https://my.subdomain.co.uk?

[TheoMer]

Hi,

So my https://my.domain.co.uk address is pointed to my heroku site and I want any instance of my.domain.co.uk or http://my.domain.co.uk typed in the url to be redirected to https://my.domain.co.uk. How do I do this?