Ok, so you just got yourself an incredibly cheap laptop for hacking around. When it comes out the factory it's a bit noisy, the HDD "hurrs", the fan spins up pretty often and battery life is around 4 hours. By changing the HDD to an SSD all of that will change, promise.
Step 1 - Order
Use the factory installed Windows 8.1 installation and Internet Explorer (obviously) to order yourself a brand spanking new SSD from any online retailer (Amazon). I personally recommend the Sandisk Sandforce SATA III 64gb 2.5" SSD (http://www.amazon.fr/gp/product/B007ZWLRSU). If that's not enough hard disk space for you then find another one, just make sure it is a standard 2.5" SSD with SATA III connectivity.
Step 2 - Remove
The next step is to remove the current HDD drive from the laptop, make sure you turn the laptop off, removing the charger and battery first. Remove the hunky panel on the front and carefully remove the WD HDD in it's holder from the laptop, mine was pratically brand new so you can even go on to resell it. Remove the HDD from the holder by removing all screws on the outer edges.
Step 3 - Install
Install the new SSD in the HDD holder the same way the HDD was in there, do it right the first time otherwise you will have to restart. Slide the holder back into the laptop and push a bit until the connectors... connect.
Step 4 - Install some more
Obviously noone wants Windows 8.1 on their laptop, so install a Linux distribution of your choice, for absolute 1337ness I recommend Crunchbang Linux. This can be done from a USB stick or for some "old school" people you can also use the CD reader that most laptops feature nowadays but never get used.
Step 5 - Results
Booting the device is fast, no noise comes from the laptop once booted, my fan hasn't turned on once, even using the laptop in poorly aerated environments (beds, cushions, that kind of thing) and the CPU core temp reaches a maximum of 50°C. SSDs have the great advantage of not being a gigantic metal disc hurling around at 5200 RPM, so they won't make a sound, and another advantage is the lower power usage, my laptop now does 6 hours of continuous web browsing and other "normal" activities with the new SSD, this will not work the same for you if you attempt to use the low-spec laptop to render an entirely CGI animated film like Avatar.