That's a full question - I'll give it a shot.
1. Puck turns Bottom's head into that of an ass.
2. Bottom's return to the other workers scares them away, and Puck gets them lost in the woods.
3. In order to prove he isn't scared, Bottom sings at the top of his voice which awakens the sleeping Titania who instantly falls in love with him.
4. Hermia is upset with Demetrius about the disappearance of Lysander (a conversation Puck and Oberon overhear) and storms away from him. After Demetrius falls asleep, Puck puts the drops in his eyes to try and correct his previous mistake.
5. Helena and Lysander's fighting awakens Demetrius who instantly falls in love with Helena also leading to an aggresive quarrel between the two men.
6. Lysander and Demetrius decide to duel for Helena's hand and leave the two women - which leads to Hermia threatening Helena and both women running away.
7. Puck gets the four lovers tired and in the same general place in the woods where he can annoint Lysander's eyes with the drops again to make everything right.