how to replace ignition lock tumbler?

when you remove the cylinder youll see the linkage inside has groves in it you need to use a screw driver to manually start the car by pushing the linkage back and forth.if you can do this the column is ok.then you must be sure the linkage is set back to off position before installing the cylinder.one grove off youll have problems.there is a line on the cylinder and one on the column they have to line up when the cylinder is installed. Heres a picture of the key tumbler

I found the problem. I took apart the whole shell of the column. Beside the gears for the lock cylinder, there was a piece of metal wire stopping the gears from turning. Apparently, it was left from a previous repair. All is good now. Thanks for your help. Its greatly appreciated.