If memory serves, most of the threads on my park tool are engaged with the crank arm, so I'm assuming the same is true with the Unior. You should tighten it by hand until it will not engage anymore. I normally get it slightly tighter with a wrench but don't overdo it because you have to back the tool out. If it hasn't been worked on for a while, you might have to "clean" the thread out with the tool. You did remove the bolt and washer first, right?