If you're using AutoCAD 2018 for your design projects, you may need to view and navigate 3D models. Here's a guide to help you easily view 3D in AutoCAD 2018.

1. Open a 3D Model: To view a 3D model in AutoCAD 2018, start by opening the file containing the 3D model you want to view. You can do this by clicking on the 'Open' icon or going to 'File' > 'Open' and selecting the file.

2. Navigate in 3D: Once the 3D model is open, you can use the navigation tools to view it from different angles. The orbit tool allows you to rotate the model, the zoom tool enables you to zoom in and out, and the pan tool lets you move the model side to side.

3. Using Viewports: AutoCAD 2018 allows you to work with multiple viewports, which is helpful when working with 3D models. You can create different views of the 3D model in separate viewports to have a better understanding of the design.

4. Visual Styles: AutoCAD 2018 offers different visual styles to view 3D models. You can choose from wireframe, hidden, shaded, and realistic visual styles to get a better look at your 3D model.

5. 3D Viewing Commands: AutoCAD 2018 provides various commands tailored for 3D viewing. For example, the SWIVEL command allows you to rotate the view, the DVIEW command lets you change the view direction, and the 3DORBIT command allows you to orbit the model.

6. UCS Icon: The User Coordinate System (UCS) icon helps you orient yourself in 3D space. It's a visual guide that shows the orientation of the X, Y, and Z axes, which is essential when working with 3D models.

7. Using 3D Gizmo: The 3D gizmo in AutoCAD 2018 can help in moving, rotating, and scaling 3D objects. It provides an intuitive way to manipulate 3D objects in your design.

By following these simple steps and utilizing the features provided in AutoCAD 2018, you can easily view and navigate 3D models for your design projects. Whether you're a beginner or experienced user, mastering 3D viewing in AutoCAD 2018 will enhance your capabilities in creating and editing 3D designs.