[Harry Potter] How does one bind their own soul to a Horcrux after committing a murder?

you bind it using a spell, at first. eventually, Voldemorts soul was just so diminished that broke and bound itself to things of it's own accord. at least that's what i believe. as to binding the souls of people you murder, no, thats not how it works. when you murder your going against nature and your own soul splits in two and if you wish, you can bind part of it to another object.