The Start screen appears when there are no documents open in InDesign. It lists your recent files (if available), presets, and more. You can also access various resources and search Adobe Stock from here.

Choose File > New > Document. In the New Document dialog box, start by choosing a preset. For example, the Print category shows various sizes and document options you can set for a new document. The New Document dialog box is where you can access free and paid Adobe Stock templates, which are a great starting point for your designs. You can find free photos at unsplash.com.