You did not specify if you are having trouble with an automatic or manual. I'm guessing manual transmission. This might be helpful.
https://www.youtube.com/watch?v=2TCHzIvAvRQ
I set all the shift ears on the trans to the middle positions then run a centering rod through the indexing hole on the side of the shifter to align the gates. After that, install each rod & make sure that you can get into each gear position fully. It's some back & forth & small adjustments that take some time but not difficult.
Always much easier with the trans & shifter out on the bench rather than lying under the truck, in the snow, with half dead flashlight and junk falling in your eyes.
Good luck.