Don't have the manual for mine and never had to look for one. Assuming that there are two clamps on your focus ring as there are on mine i simply adjust focus and then move the clamp to that position and lock the screw at the bottom of the clamp. Never bottered doing the adjustment at more than one magnification as it seems to stay in focus no matter how close or how far away from the paper i adjust the head. You can use the other clamp for another focal length or lens so it is easy to swap by just moving the focus ring to the other clamp.
The enlarger will focus no matter what brand of lens you use. I use either a 50 2.8 Nikon or a 50 4 Focotar, there's a bit of a difference between the clamps for those two lenses even they both are 50mm.
Hope this make sense?