Hi Sinclair Family! Like bubbles said, the Gallery is the best place to find a house. Make sure you know the size of the lot you want to place the house on. From map mode, in the upper right of your screen is a button with two photos, click on it, and it will take you to the Gallery. Click on Community then on the left side will be the categories, choose Lots. Then below that, click the + by Advanced and there you can narrow your choices by lot size and/or price. When you find the house you want, and have brought up the details screen it is as simple as clicking "Bring Lot Into Neighborhood" on the lower right of that panel then place the lot.
I believe you can also save the lot into your library and place it that way as well.