This might be too gooner but how do you start the 18+ stuff
Basically if you ever see a Heart Balloon icon over a person or object, that will contain some kind of lewd event. The most obvious ones are located in the Merchant Camp. Some of them are available right out of the gate, others are tied to completing side quests (like catching fish for the Fisherman NPC.). There are also several that can just occur depending on certain choices you may make. Certain glowing effects near water or beds may also indicate that you can view a scene. Hope that helps!