This achievement requires that you have 5 Sims promoted to the Mad Scientist rank at the Science Lab. In order to obtain this achievement, you need to first build the Science Lab in your town. Once complete, you can send your Sims to work there. From the Simtracker, select the briefcase icon for jobs. Then accept the Science Lab job with a Sim. Your Sim will earn Job XP and level up. In order to pop this achievement, a total of 5 Sims must reach max rank, Mad Scientist, at the Science Lab. There are three ways to earn XP towards this achievement:
Play games of chess - This is the best method to rank up for this achievement. You can purchase a chess board from the Living Room section of the Home Store for $300 (or they are available within the Park if you build that in your town). Up to two Sims can play on the same chess board simultaneously. You just need to have correctly positioned chairs available at the chess board table. Each round of chess takes 10 minutes. It will take less than 20 games of chess for a Sim to level up to Rank 5 from Rank 1.
Go to work at the Science Lab - Your Sim will earn a small amount of XP for completing a day of work
Use the telescope - You can also earn XP toward the Science profession by using the telescope. However, each telescope costs $70,000, so don't even bother with this. Use the chess boards.