Just click on the screen to interact; items you take will appear in your inventory, and to use them, just click once on the item, and then again whenever you want to try using it onscreen. The biggest issue for some players might wind up being having to troll the screen with their cursor looking for hotspots, since it isn't always visibly apparent when a portion of the screen will have an area transition or something to interact with. The game is also fairly short with relatively straight-forward "use item here" puzzles, although if you want to stroke your own ego you could just convince yourself that any ease is because you missed your calling as an International Man/Woman of Mystery. (Yeah, baby!)
But these are admittedly minor quibbles with what is a solid bit of adventuring to get you in the right frame of mind for your weekend. (You never know when you're going to need to infiltrate something.) The artwork is gorgeous and moody, even if the darkness might be a little hard on your eyes, and the atmosphere is that perfect blend of creepy/desolate that makes for great evening gaming. The ending is a little abrupt, but if you're looking for a tasty bite of What If?-style point-and-click gameplay, you could do a lot worse than Owl's Nest.