We always apply a dab of silicone dielectric grease to ease plug wire boot installation and removal. Too much grease and the boots want to slip off. A dab the size of a wooden match works best. On at least half of the plug wires, we had to grab the terminal in the spark plug end and pull it out to meet up with the edge of the boot where the size increases to accommodate the spark plug porcelain. You should feel a click when the plug wires are installed properly.