If you’re using a Nylock or other kind of locking nut you’ll probably need to spin the pivot nut on with an impact wrench until it pulls tension on the pin.
The threads on the end of the pin in your picture are pretty shiny, you might need to dress those up as that will cause you issues too. The more resistance you get from the threads the harder this will be.
You can also try grabbing the outside of the shoulder on the pin (the part up against the bushing in the picture) with a set of channel locks or vice grips. But you have to be careful not to bung up the bushings when/if you do that. Or any part of the shoulder that will touch the bushing, but the outside ring of that shoulder shouldn’t touch anything.
I use a battery powered impact to get mine started, and prefer using a regular nut with a lock washer. The Firm Feel pins I use call for a 100 ft/lb torque spec, so, I don’t worry about them backing off or about starting them with the impact.
