There were few exceptions to a Navy requirement that carrier-based aircraft be self boarding, i.e. a separate ladder was not required. For more background on this, see:
https://thanlont.blogspot.com/2015/10/carrier-based-airplane-self-boarding.html
https://thanlont.blogspot.com/2011/09/self-boarding-for-douglas-skyhawk.html
The F-111B was not an exception:
Note that the bottom step is wide enough for both feet. Not obvious in the above illustration is the second step, a peg extended from the forward side of the brace going from the fuselage to the aft end of the bottom step.
Note the inflight refueling probe location in the illustration above is the original one. Also see https://tailspintopics.blogspot.com/2012/01/f-111b-inflight-refueling-probe.html
The third step, also a hand grip, is a peg that extends out of the fuselage just below the bottom of the crew-escape capsule.
To board from the left side after opening the canopy, it was left foot on the bottom step, right foot on the peg on the brace, and left foot on the peg on the fuselage. It would appear that the next move, getting the right-hand leg over the canopy sill, could be challenging for a short person.
The door that housed the bottom step was a little wider at its aft end and a little shorter than the nose landing gear door and centered slightly aft (the aft end of the "ladder" door is located forward of the top of the aft stripe on the landing gear door) along it.
Self-boarding was utilized during the at-sea trials.
According to Jim Rotramel, my F-111 subject-matter expert, most USAF F-111s did not have the retractable "ladder" door: "The only thing common to both variants was the retractable peg in your fourth pic. It served as an anchor for our boarding ladder, fitting into one of two slots, depending on which side the ladder was being used on. It was ‘interesting' to go to a base that didn’t have our boarding ladders, mostly they resorted to step-ladders."
Jim Rotramel
However, it appears that the F-111As were initially equipped with the ladders but they were subsequently removed and follow-on USAF F-111s were delivered without ladders except for the FB-111A. Bill Spidle provided this front view of one at Offult AFB taken by George Cockle on 14 December 1980. Note the angle of the "ladder" door (it was attached by goose-neck hinges on a tangent to the local cross section of the fuselage, which was identical to the F-111B's for the length of the nose landing gear door). What appears to be a widening of the door as it gets closer to the fuselage is actually the inboard side of the brace behind it.
And this FB-111A boarding ladder from the side:
