Thank you Anthony.
Now, @Betterlatethan, you have many things to record yourself but, of course you'd need microphone first. If you have a webcam with already in-built microphone, it will do just fine. You're not going to do proffessional recording so you don't need too high techy things to do this.
Windows itself has in-build voice recorder on your computer which can record short recordings and (as much as I know as I don't use that too often) you can save them unfortunately just in .waw format. This is actually not that bad either as it is the most raw sound recording you'd ever have.
However, Audacity is the most common free software many people use for making their recording and also audio editing so I'd maybe explain some things about this.
First of all you have to install the software which you can find here. So, Step 1: Download and install the software. In the mean time I'll prepare the tutorial for you and put it online but if you're in a hurry Audacity has its own tutorial too which could be find here.