Unfortunately, you can't put up billboards in the traditional sense in The Sims Kingdom. The game focuses on building and managing a theme park, and billboards aren't a typical feature of those environments.
However, you can achieve a similar effect by using these techniques:
Remember, The Sims Kingdom doesn't have the same level of customization as other Sims games, but you can use your imagination to create a visually impactful advertising effect using the available tools.