Get a cable that has 2 RCA phono plugs on one end, and a 1/8" stereo plug on the other.
Turntable => phono preamp => mike input on Macbook (second little hole from front, on left side).
Audacity is free software for making digital recordings.
In system preferences, sound panel, set input to external, turn gain all the way down.
If you have a stereo power amp, you only need a volume control between the phono preamp and the power amp. http://phonopreamps.com/
have phono pre-amps with volume control, at reasonable prices.
Keep them spinning.