@jinxD21 You don't need to buy a second copy of the game. Your Origin account owns it, not your computer, and you have the right to install it on as many systems as you want. Just open your Origin library, click on the Sims 4 icon, and click the orange Download button.
You can only play on one computer at a time, or rather you can only be signed into your account on one computer at a time. But there's nothing stopping you from installing on both your laptop and desktop and switching back and forth whenever you feel like it.
