First, you can just click Window > Workspace > Reset (whichever workspace you use, probably Essentials). That will snap everything back to how it was when you first installed Photoshop.
Otherwise, you should be able to drag any panel to the bar on the right side of your display. You'll see a teal line highlight to indicate where it will dock -- horizontal bars mean it will dock as an icon while vertical bars show where it will dock as a full panel.
Finally, you can always dock a panel with another group of panels, so that the added panel is another tab. This time you'll see a teal box highlight to show which group your panel will be added to.
I hope that helps -- if for any reason this doesn't fix your problem, please let us know! Thanks, David