The site I linked you to says your laptop supports up to 8GB of ram, it also links you to a 4GB memory module available for purchase from 3 different vendors.
You should only add memory if you currently have only 4GB installed. Here is how you can check to see how much memory you have installed.
If your laptop is using a Hard Disk Drive and not an SSD, then upgrading to an SSD would be another option.
If you go this route you can use Macrium Reflect to clone your disk.
Alternative ways to speed up your computer recommend by Komando.com