To design the user interface, begin by selecting the Main.storyboard file to load it into Interface Builder. Drag and drop a UIPickerView from the Object Library (View -> Utilities -> Show Object Library) onto the view and position it at the bottom of the view. Also add a label and text field. Stretch the right and left hand edges of the label until the dotted blue margin line appears. Using the Attributes Inspector (View -> Utilities -> Show Attributes Inspector), configure centered alignment on the label and reduce the font size to 12 point.
Select the text field and change the Keyboard property in the Attributes Inspector to Numbers and Punctuation, then change the Placeholder setting to US Dollars (USD). Once completed, the view should appear as illustrated in the following figure: