Those are the adjustable "top link" and "side link". They are meant to be hand tightened, and you do not normally use a tool. If you are attempting to tighten them when there is weight on the 3-pt hitch and find it difficult, you should take the weight off the hitch first. Also be sure the threads are properly lubed -- if rusty, these are a pain to work with even when unloaded.
I am sure you could use the loop end of an adjustable wrench or box wrench to crank on the pins, but they won't take a whole lot of force so go easy. Really, if the adjuster is that hard to turn, you need to relieve the load first.