.. General Game Info
This is a classic (not to say retro) point-and-click game. When you want to look at something, right-click on it; when you want to interact with it (pick it up, talk to it, use it), left-click on it.
Hover at the top of the screen to see the menu, which for Rosa contains her phone, her inventory, and the Options menu (where you can save and load games, see your achievements, and adjust some of the settings). You'll see that there are more settings available than in the previous games, though they're still pretty primitive.
In this game, you can switch between being Rosa and being Joey. To change from one to the other, either press the Tab key or pull down the menu and click on R or J. Joey's two abilities, blowing on things and using his tie, are usually the only things in his inventory; to use them, drag the breath or the tie onto the item you want to use it on.
It should be noted that you can't play the game in a window. Pressing Ctrl-Esc during the game will drop you to the desktop, but the game will be chucked when you come back to it. If you need to check something on the desktop, it's better to save your game and close it, then restart and reload when you're done.