I've found that iTunes is by far the easiest most user friendly software for burning CDs.  You can download it free at: http://www.apple.com/itunes/download  After its installed then open the program and... 

1. At the bottom left corner of the screen you'll see a plus "+" sign.  Click on this and in the new folder type in any name you desire.  This is your new CD burning playlist!

2. Now look the top right corner of the screen and you'll see word "File".  Select it and beneath it you'll see "Add File to Library".   Click on this, and FIND your mp3 file(s) on your computer that you wish to burn to your blank CD.  Import these into your iTunes music library.  Shortcut: You can also manually drag and drop your mp3 files directly into your new playlist, from one screen to another.

3. Now above your new playlist you'll see the word "music" which is directly under Library at the top of the left column on the screen.  Click on it and you'll see your new mp3 you added on the right side.  Click your mouse on this file (holding the button down) and drag it and drop it into your new playlist and you're done!

4. Just click once on your new playlist to highlight it, and in the bottom right corner of the screen you'll see the button "Burn Disc".  Insert a blank CD and click this button and you're done!! 

Instructions to burn a CD with Windows Media Player. 

This software is also free and can be downloaded at: http://www.microsoft.com/windows/windowsmedia/default.mspx  After its installed then: 

1. Open up windows media player and select the "File" menu choice on the top left corner of the screen.  Scroll down to "Add to Library" and choose the MP3 files that you wish to burn to a CD.

2. After they are added, click on the button called "Edit Playlist" on the top left section of the first Windows Media Player screen.  A box will pop up, and on the LEFT side of that box you should find your files you just added.  Double click on them until they show up on the RIGHT side of that box.

3.  Insert CD into your CD-ROM burner and click "Start Burn" on top left corner of screen.

That's it!!  See wasn't that easy?

Have fun burning many wonderful CDs!!

p.s.  If you get stuck you can always click here for a variety of other ways on "How to Burn a CD!"...enjoy!