All you need do is go to the "New Profile" link at the very top of any page when you are logged in. Once there, click on the "unrelated people form" link.
Make sure you have your friend's correct first name and birth name and email address. Once you've enter just those 3 items, a box will appear in which you can send this to your friend, at their email address, as an invitation. They should then remove you as Manager/ Trusted at the Privacy tab on their Profile and you will also need to remove them as a Trusted at the Privacy tab on YOUR profile.
Hope this makes sense - it really is quite easy.