The 3D preview lets customers see their personalized design on a 3D model of the product that they can rotate, instead of a flat picture. It's in Beta, so models and features may change.
Step 1: Open the 3D preview
In the editor, click 3D next to your previews below the canvas. If the set isn't using 3D yet, you'll see a list of models.

Step 2: Pick a model
Click the model that matches your product, for example T-Shirt, Mug 11oz, Hoodie or Tumbler. Enable 3D is ticked automatically, and the panel shows the model and how many print areas it has. Click Change to pick a different model.

Step 3: Map your designs onto the model
Under Print areas, each part of the model (for example Print area 1 and Print area 2) has a dropdown. Choose which of your print files or previews should be printed on that part, or leave it as Not printed. Click Edit to adjust how it sits on the model, or Add print area if you need another one.

Step 4: Check and save
Drag the model to rotate it and check your design from every side. Click Reset view to go back to the front, then click Save.