To get the quest for the next scene you have to get a certain number of stars. To open new scenes, however, you also need more reputation, which you get by having stuff in your garden. Click on the build button (picture of a saw) and buy more more stuff worth more reputation to put in your garden. For the second poster, you have to complete each scene many times to get each star, though the better you do the faster you collect points towards the next star.