Connect your turntable to your computer. Most modern turntables include red and white RCA jacks. You can connect using an RCA-to-3.5mm cable (the 3.5mm plug connects to your computer's Line-In port), or an RCA-to-USB cable for cleaner sound quality. If you have an external sound card (audio interface) with RCA jacks, you can connect it to your USB port or FireWire port and then connect RCA plugs to the interface.
Open Logic Pro (Macintosh HD > Applications > Logic Pro) and select your input source. Click "Logic" in the upper left corner of your screen, and select "Preferences" and then "Audio." On the "Input Device" menu, select your USB device, if applicable. If connecting through your "Line-In" port, select "Built-In Input." Click the "Apply Changes" button.
Create an audio track for your recording. Click the "Track" menu at the top of your Logic Arrange window, select "New" from the top of the list and choose "Audio Track" when asked to designate your track type. Tracks are the spaces (appearing as long horizontal bars) onto which you record audio waveforms.
Press the red "Record" button at the bottom of your Logic Arrange window. Immediately afterward, start playing your LP to begin the audio transfer. When you reach the end of the song or record side (depending on how you want to divide your recordings), press the "Stop" button in your Logic Arrange window.
Open your mixer by clicking the "Command" and "2" keys simultaneously. First, select your track on the channel strip (indicated by the same number that appears in the left column of your Arrange window). To raise the volume of your recording, drag the "Volume" slider upward along its vertical line. To master your frequencies, click the "Channel EQ" box and move the line on the graph up or down to increase or decrease your bass sounds (the left side of the graph), mid-tones (center of the graph) or high treble sounds (the right side of the graph).
Export your LP recording as a digital music file. Click "File" on your menu bar, select "Bounce," enter the title of your song (or album, if recording more than one song into a single file) and choose an audio format from the list. Click "Bounce" in the lower right corner, and Logic will begin the process of converting your recording into a self-contained audio file.