i'd start off by watching a youtube video and buying grafting tape. You take a clean razorblade and put some rubbing alcohol on it, cut a snippet off of a healthy looking branch of an avocado that you know produces fruit. Then, you make the same angle cut on the stem of your sprouted avocado, put the cutting on there and wrap it up with grafting tape. once it heals, kill off the other side (other genetics) of the original tree and then you have a clone of the fruiting tree that you took the original snippet from