By leaving everything loose. What they mean is everything. The nuts that hold the rubber to the cross member, the bolts that pull the center assm. tight to the cross member. Then you start all of the bolts to the tranny. Now tighten everybody up before you jack the cross member to the body. Use a drift punch to line the holes up as you jack it up. With the punch in one hole install and tighten the other one up. This will leave the remaning hole lined up. You will need a long extention and a 1/2" wobble socket to tighten the nuts that hold the rubber to the cross member. There want be a bar going to the bell housing on a 71.