You need to place floors in order to be able to place objects.
Hey!
I'm sorry. I've been really busy and haven't had enough time to finish alpha 8. But we haven't stopped working on it. Alpha 8 is almost done. Once we have finished the save system (we've changed how AI works, and that means that we've to re-do AI saving) we'll publish Alpha 8. But I'm sorry I can't tell you a date. As soon as Alpha 8 is done, it will be released.
Thank you for your interest!