Set a Start Point to decide exactly where a prototype begins — add multiple ones to create separate prototypes within the same document.
Setting a start point
To set a Start Point, open your prototype in the Preview window, select a frame from the drop-down menu, and click 
. You can also set a Start Point for a prototype in the Prototype tab of the Inspector by selecting the Set as prototype start point checkbox. Sketch will also automatically create a Start Point when you add your first Link.
How to add a prototyping Start Point to a frame
Whenever you preview your prototype, you’ll always start with the frame you’ve set as your Start Point.
To remove a Start Point, select the frame in the Preview window and click again, or deselect the Set as prototype start point checkbox in the Prototype tab of the Inspector.
When nothing is selected on the Canvas, the Inspector shows all Start Points in your document, so you can see and navigate to them without hunting through the layer list.
How to set a Start Point from the Preview window
Setting multiple Start Points
You can set more than one Start Point to guide your users through different aspects of more complex designs, such as a sign-up or user settings flow, for example.
Every time you set a new Start Point, it’ll appear as a different prototype in the same document in the web app or the iPhone app.
