You can convert your vinyl discs to MP3 by using software such as Audacity.

Connect your turntable to the computer with an RCA cable into your sound card line-in input.

Launch Audacity and create a new project by clicking "File" then "New." Change the recording input to "Line-in" from the drop-down menu next to the volume faders. Make sure the volume for the microphone input is set to max by sliding the fader.

Click on the "Record" button to begin recording in Audacity, then start playing the vinyl on the turntable. When the album is finished, press the "Stop" button. In the "File" menu select "Export to MP3." Name the file and save it. That's all there is to it.