Auto Trans Linkage Adjustment?

[AgBoy]

I have a '99 Silverado with the auto trans. I just finished swapping the tranny myself (very involved task) and the only thing i have left to do is adjust the shift linkage. Currently the transmission will shift into all gears fine but will not go into Park, it goes "in-between" Park and Reverse allowing it to coast. If i get under the truck i can tap the lever on the transmission into Park where it stay until i take it out again. From what i have researched i know that the adjustment is to be done with the plastic cylinder part way down the cable, but i cannot figure out how to make it move to adjust it. If anyone could give me some pointers on how to fix the issue, they would be GREATLY appreciated.