Checking your VPS CPU and RAM usage is important because it shows you how much computing power is remaining on your VPS. When your CPU or RAM usage is high it is a sign that you are running out of power on your current VPS plan, and an upgrade to a more powerful plan might be needed. 

Step 1 - Right click on the blue bar at the bottom of your VPS screen. When the menu appears left click on "task manager"

Step 2 - When the task manager program opens click the "Performance" tab on tabbed menu bar. You will then see the CPU and RAM (memory) usage for your VPS.

If you see that your CPU or RAM usage is reaching 100% for long periods of time it is an indication that your current VPS plan is not powerful enough to keep up with the software you are running on your VPS. You will either need to lower the software you are running, or upgrade to a more powerful VPS plan.