A brief recap: Lear had planned to spend his retirement with Cordelia. Obviously, that's not happening any more. So now he's spending alternate months with his remaining two daughters.
Things are not going well at Goneril's castle. Lear's a lousy houseguest—he continues to act like he's in charge (even though he gave up his kingly title). Also, Oswald tells Goneril that Lear smacked one of her servants upside the head because the servant was rude to Lear's Fool (Lear's personal comedian).
Not to mention Lear's entourage—a group of a hundred knights that the King brings everywhere—is a rowdy bunch. (Hmm. If Lear was serious about retirement, why the heck does he need an entourage of knights?) Goneril is fed up with all of their antics.
She tells Oswald, her personal assistant, to be rude to Lear in order to spark a confrontation. This way, they can air everything out. Goneril also announces that Regan and she share the same distaste for their father, so she's safe if Lear goes to Regan for help.
Goneril announces that old men are like babies again, and can therefore be manipulated easily.
Goneril reiterates her plan to be rude to dad so she can have a stern talk with him.