That item will still be selected as long as you don't take some other action along the way. Next, select the Items tab along the right side of the screen (it looks like a shopping bag), which will return you to the page from which you purchased the item in question. Buy the item once, then place it wherever you like. Once you're ready to begin, enter Buy Mode and purchase an expensive item (it works best if you can barely afford just one of the item, such as especially expensive appliance).
Before you start, it's a good idea to save your game progress in case you make a costly mistake. Follow these directions to earn a bunch of money.