If the crossbars are new they should have instructions as to do it. From what I remember they had a slide mechanism that tightened down with a plastic screw. Theirs a groove in the top of the bars already installed on the roof. I don't remember if I had to remove the rear piece of the installed bars or not to install the crossbar slider. I don't think so, I think they just go in the groove and turn. Mine have been up there for years and have a roof pod attached. I can't really answer your question better than that but I can take some pics after work if it's still daylight. This is all from memory, so not really reliable. So I'm told... LOL
