Follow the instructions on the left and click on the hyperlinks as you proceed to see helpful visuals here
You have two choices to switch keyboard layouts using two-key combinations. This means that you must press the two keys together to make this work. Doing this will switch your keyboard layout back and forth between Spanish and your default layout (e.g., English).
Now, in reality you don't have to press them both at exactly the same time. You can press one, say the LEFT ALT key, and while keeping your finger on that key then press the SHIFT key.