The agitator coupling in my washer was stripped out.

I had already removed the old coupling by removing pulling the agitator straight up off the coupling, then I removed the bolt that held the coupling in, and pulled the coupling up off the shaft.
I placed the new coupling on the shaft and pushed it down until it seated, put in the new bolt that came with the coupling, replaced the agitator, and was washing clothes within 10 minutes.
On time delivery, right part, complete with instructions.
Good job.