Now its time to install the GPU, this will require some of the back plates being taken off before hand so the output ports can be revealed out the rear of the pc case so the user can connect their peripherals. So check the GPU manual for how many plates you will need to remove. Be careful with this process as some have to be snapped off and cannot be replaced if you pull the wrong cover off. When you have the covers of, just like the ram, you can align the graphics card with the PCI-E slot and the noth within the port, you can now apply pressure and push it into the port, again, not too much pressure, you should hear the small click of the locking mechanism to keep it in place. After this is done you can apply additional reinforcement by screwing the top of the graphics cards backplate to the PC case, now the GPU is secure and will not wobble around when moving your system.
These are two really simple steps. The DVD drive will slide into place and is secured by two screws on the side of the component. When installing the cooler most come with pre-applied thermal paste so its not necessary to manuall place it onto the CPU. After this its just the simple snap of four buttons and its locked onto the motherboard until it needs to be removed.
You can now insert the PSU into the system. If you have a modular PSU no cable management will be necessary at this stage as you dont yet need to plug in any cables. But with a non modular power supply its probably best if you run the cables through a hole into the back of the system. This will ensure you dont have anything in the way blocking you from inserting parts into your machine and getting in the way. After this you are going to need to mount the PSU to the PC case so that it doesnt slide around when moved. Its important to remember not to screw too tight again, it isnt necessary and will only cause problems in the future.
Now its time to install the HDD, the HDD is one of the easiest components to install. All you have to do is slide the HDD into the designated slot, most cases have a locking mechanism so that is all thats required. For some older cases the HDD will slide in but will require multiple screws in order to be locked into place. If this is the case then dont tighten the screws too tight as you want to easily be able to replace it if necessary. The cables can be inserted later all at one time so they arent getting in your way when you are inserting other components.