Step 1: Go to Your Room
To edit your room, you first need to get to your room listing. There are two ways you can do this. The first way is to go to the Map -> My Rooms -> List My Rooms. The second method is to go to the Dream Isles -> The Isle where you room is listed -> scroll down to where your room is.
Step 2: Editing Your Room
After you scroll down to your room, you will notice that there is an "Edit" option on the right-hand side. Click the "Edit" link by the room you want to edit.

After you are in your room, look to the right-hand side of the screen again. Under "Special Room Commands" is "Edit the player size and movement map." Click that.

Step 3: Editing Where People Can Stand and Pose Size
After you click the link previously mentioned, you should be transferred to another screen that shows a small version of your room. If this does not show up, try refreshing the page. If it does not show up again, try clearing your internet cache and check your firewall settings, then go through the step processes again. Also make sure that you have the latest version of Adobe Flash installed. If it still does not load after that, open a Problem Ticket.
For the sake of this tutorial, we are just going to do a large square over the entire room. Click in each corner of the room in order with the left-mouse button. To undo a click, click the right-mouse button. I started in the lower left-hand side. You can do multiple areas where people can stand in a room, it is just the same process except in smaller areas.

By the time you click the third corner, a shape like this should appear on your screen. Click on the final and fourth corner.

When you are done, there should be a giant red square over your entire room. If this is where you want people to be able to stand, click "Continue."

The next image that will be brought up shows two wolves. Using the arrows beside these wolves, you can edit how large or small poses will appear in your room.

Your room should now be covered in a green layer. This shows where people will be able to stand in your room. If you are happy with what is done. Click "Done!"

Another little screen will pop up asking you to confirm the changes. If you are okay with them, select "OK." You will the be transferred back to the Room Edit image (the second screenshot). You can then enter your room and test it out!

And that is how you edit where someone can stand/move in your room. Hope this was helpful!