In order to unlock this achievement you need to win a game of 8 ball. In order to win a game of 8 ball, you have to pot all of your balls, whether it be stripes or solids, before sinking the 8 ball. Once all of your balls are potted, you can then sink the 8 ball. This can be done in career, or multiplayer. The following video shows a game of 8 ball from start to finish.
Video credit goes to dennis585.
I hope this solution helped! Leave a comment letting me know if there is any room for improvement! Thanks.