Would recommend a good book on basic instrument flying.
Be on speed, trimmed, and configured at GS intercept. Lower the nose 3 deg from where it was in level flight. Decrease power slightly to hold airspeed constant. Crosscheck the VVI after stablizing in the descent. It should be about 600-800. (Miles/min x pitch = VVI; e.g. 2 mpm (120k) x 3 (GS angle) = 600)
Your attitude indicator and power setting are your primary "control" instruments. Airspeed , VVI, Hdg, and Altimeter are your "performance" instruments. Set your control instru and crosscheck howzitgoing on the performance instru. Make small changes of 1-2 deg in pitch or 2-3 in roll to keep from S-turning or wandering through the GS.
Again, recommend a good book or better yet, go see your local friendly flight instructor for the real thing. You'll love it.