How do Jedi Become FORCE GHOST and WHY?

We all know that Obi Wan Kenobi didn’t really die after facing off against Darth Vader on the Death Star, and we also know that Yoda and even Anakin Skywalker were all able to achieve a similar state and become force ghost. But how does one reach this ethereal state? Well we need go back all the way to Qui Gon Jinn the first jedi in modern star wars history to become one of with the force.