You don't really, you would replace the entire linkage. Best place to get it from and be correct the first time would be your dealer.
You have to remove the linkage from the wiper motor.
Its best to consult your owner's manual. It will have a chart.
I have the same problem and came here looking for answers, lol. One thing I did do for a temporary fix was to reattach the arm into the worn bushing and then use cable ties around the arms to hold...
on the end lift up hard that is the cap covering the nut remove nut and lift. if it wont come off try using WD-40 or other...hope this helps