To look at the inside of your computer, you must first remove the outer casing.
First unplug everything from the back. Then remove the 4 or more screws on the back that hold the case on. There are lots of other screws visible, so be careful to get just the ones that hold the case together.
[Some cases do not have screws. The side panels slide and then lift off. It can be hard to tell what slides which way.]
You'll likely need a Phillips-head screwdriver for this. That's the kind with the X-shaped tip. Put the screws where you can find them again when you're done and where you won't step or kneel on one. They do hurt!
Once the screws are out, the case should slide off. Some cases need to be lifted up in the back a little so you can pull a lip loose at the front edge.
Now you can look around inside.
Ground yourself by touching something metal like the power supply or metal parts of the case before touching ANYTHING inside the computer. Static electricity kills computer parts!!!
Some people wear a special wristband to discharge static as they work on computers.