Templates 
are a great way to start a new project — rather than starting with a blank canvas you can start with a document that already includes Artboards, placeholder content and more. They’re also a great way to give everyone a head start on repeatable work, while improving consistency across your design documents.
By default Sketch includes templates with ready-to-go designs for presentations, social posts, mockups, business cards and so much more.
You can also turn any of your own documents into templates, which will make them available for anyone in your Workspace.
Creating Templates
To create a document from one of these templates, head to the Workspace window (⌘O), and click Templates in the sidebar. You’ll see a grid view of templates — double-click on any of them to create a new document from that template and start editing.
To turn a Workspace document into a Template, go to the Document’s Settings File > Document Settings or press ⇧⌘,. In the General tab, set the document as a Template.
For local documents, you’ll first have to upload it to your Workspace. To do so, drag your local document into the Templates section of the Workspace window.
Getting the most out of Templates
There’s lots of ways in which Templates can be useful for you and your team, but here are a few general tips:
Working with images
The built-in templates make extensive use of images, but can also add your own photos. Simply, drag and drop an image from the Finder or Photos app onto any layer. Sketch will replace either the image fill or resize the image layer to fit the new proportions.
Working with Libraries
Libraries are a great way to reuse existing elements and give yourself a headstart. However, you may not always want all your libraries to be enabled at all times. For example, if you design for both iOS and Android you likely have different libraries for each platform. Set up the right libraries for each document and then save it as a Template. From now on, each iOS or Android project will have the right libraries enabled from the start.
This way, you no longer need to remember whether you enabled or disabled the right Library when switching documents — Sketch will do the work for you.
Creating custom previews for your template
You can give your document a custom preview that will appear the web app and Workspace Window. By default, we’ll use the first Artboard in the document, but you can change this at any point. In the Mac app, right-click on the Artboard you want to set as thumbnail and choose ‘Set as Thumbnail’ from the menu.