Can anyone tell me how to put floors, wallpaper and even furniture on my expansion. I am at a loss. Thanks.

Hi there Carrie!  the expansion is handled the same as your original grid - you hit the ITEMS button, which is to the right of your friends list, the top right button. That will expand all the stuff you can buy - walls and floors are in the tabs that appear on the left.
If you have any further problems let me know.

It wont add the new floor i buy to the expansion. if i buy a new floor it puts it over the existing floor and leaves the expanded part blank.

Carrie - thank you for bringing this to our attention - we will look into this right away.

Hi Carrie!  Are you looking at the side-walk? It is a bit hard to tell, but the grid expands, and the floor expands with it - the new tiles that are added are along the back wall.