I got this achievement completely by accident
In order to unlock the "You're Gonna Eat Lightnin'" achievement make sure you have SOME building that you can hire staff members at your park. (I.e. Janitor, Zookeeper, etc).
Once you have that building, go in and hire a staff member that has only 2 stars. After hiring that person, click on their name and select the training offer. This should not only unlock the You're Gonna Eat Lightnin' achievement, but your staff member is now a star level 3.
**Do bear in mind, the higher the level the staff member, the more they cost you in salary; but you get what you pay for
- they do a more efficient job in your park!