Original: Figaro then arrives and hatches a plan to trick the Count: Susanna will give him a note indicating she wants to meet him that night in the garden; Cherubino will be waiting there, dressed as a woman; and the Countess will arrive and catch him red-handed.
Simplified: His plan is that Susanna will give him a note which says she wants to meet him that night in the garden; Cherubino will be waiting there, dressed as a woman so that the Count thinks he is Susanna.