Connect the turntable to your DAW and test to make sure the sound is registering on the desired track. This will be different depending on your set-up, so check your owner's manual, if necessary. This is an optional step if you want to have different kinds of scratching included in the loops. Record several takes of individual scratching phrases. Save and export the file as a WAV.
Set the right and left locators in the DAW to the length of the loop you want to make as well as tempo. This will generally be one, two, four or eight bars. Set the phrase to loop. Make sure that the audio part snap is set to a low increment such as 1/8 or 1/16. This will make moving audio parts easier during the editing phase.
Label the tracks then import the audio files separately into each track that will be used. Mute all the tracks but one. Set the song cursor to the position of the part of the audio file that you want to use. Play the section then set the cursor back near the beginning. With a cutting tool, cut a little before the beginning of the starting point and a little after the ending point. Delete the excess.
Move the part in between the locators where it's supposed to go and press play. Listen to where the loop is off time. Zoom in to the beginning or end of the file and trim what's necessary. Keep stopping and playing, checking the timing of the loop. Repeat the process for each subsequent file. Once the loop is complete, export the file in .WAV format.