One major example of farce in Lysistrata is Lysistrata's plan to stop the war. She believes that if all the women decide to stop having sex with their husbands, it will bring things to a close. This is clearly highly exaggerated and meant to be humorous. However, the women ultimately decide to go with the plan after a Spartan woman supports it, despite their initial misgivings. This sets the stage for the rest of the tale.
Another example of farce is the way that women punish men who oppose them. After they take the Acropolis, the men of the community decide to start a fire so that the smoke will force the women to emerge. They aren't having that, though. The women dump pots of water on the men's heads. Later, the magistrate who tries to go against the women also has a pot of water dumped on his head.
The use of a nude woman to convince the sex-starved men to finally sign a peace agreement is also farcical. As Lysistrata tries to convince the Athenian and Spartan men that fighting together isn't the right way to move forward, a nude woman is standing there. She's meant to be the goddess of peace. Since the men haven't been able to have sex with their wives, the sight of the nude women frustrates them and pushes them closer to peace. The final push of a little liquor is all that's needed to finally make peace between Athens and Sparta a reality.