QuestLine is about learning who can provide certain items and how you can use them to procure other, more interesting items. The goal is to find as many routes through the game as possible -- even the ones that end in a gruesome death.
Click on locations to visit them from the travel screen.
Once you are at a place, you will see three tabs on the bottom of the screen. Use these tabs to switch between items, places, and people. Click an icon to ask the person on the screen about the object you clicked.
If you want to try and give something to someone, or use an item on a creature or object, drag it from your inventory onto the target.
To pickup items from a room, just click on them.
A quick note:
I should mention that the number of endings you've seen should be saved, so you're most definitely not obliged to find them all in a single visit.