Hello, Doug, welome to the forums!
WOW, you mean you had one of the greatest platform games of all time for three years and never played it? I'm happy that you can enjoy it for now on
Ok, now let's go to the help: [B]in the screen you described, you need learn how to to make a RUN-JUMP.
First, hold the -SHIFT- key, then press the right ARROW. Abe will start to run right.
Second, right after staring to run, press SPACE to jump. That.'s it! Abe will perform a hideous RUN-JUMP movement, and he will hopefully grab the upper ledge.
Now, get back to the surface.
This first time, don't try to save every single mudokon you find, because that can be very frustrating. Rescue mudokons as much as you can, but don't waste a whole afternoon trying to figure out how save them all. You can try it later, after finishing the game once. I still play Abe's Oddysee and Abe's Exoodus just for fun, even having finished the like a dozen times