Get yourself an internal 2.5 inch drive of 500Gb or more size and a drive caddy. Plug it in to your laptop via the USB port. Download Acronis True Image - you get a month's trial for free - and use it to clone the internal disc to the external disc. Open up your laptop, remove the existing hard drive, replace it with the hard drive out of the caddy, close it all up and switch it on. Voila, you now how 250+Gb free on your laptop. Just make sure when you buy it that the hard drive connector of the new disc is the same as the internal drive.
Given that the OP has very liitle knowledge of computers, I would very strongly advise against this route!
Netbooks aren't like desktop PCs where removing 6 screws leaves you with a HDD in your hand.

