For laptops you can usually unscrew the screws on the underside of the laptop and slide out the Hard Drive. HDD's are usually on the front left or front right of the laptop so look for a section that may look like it could be pulled out. If you can see that locate the screws on the underside and slide it out. Be careful when doing this, dont force the HDD it should come out quite easily once you unscrew it.
Once you've done then, take off the plastic bumper part that you held onto to pull out the HDD, screw that onto the new one and slide it in.
Have you confirmed this HDD is compatible?