If you're working with 3D models, you may come across OBJ files that you need to open in AutoCAD. Fortunately, it's easy to do with the following steps.

1. Launch AutoCAD: Start by opening AutoCAD on your computer.

2. Go to 'Insert' Tab: Once AutoCAD is open, navigate to the 'Insert' tab in the top menu.

3. Choose 'Import' Option: Click on the 'Import' option in the 'Insert' tab to open the file browser window.

4. Select OBJ File: In the file browser window, locate the OBJ file you want to open and select it.

5. Set Options: After selecting the OBJ file, a window will appear with import options. Here, you can specify scale, rotation, and units for the OBJ file as per your requirements. Make the necessary adjustments and click 'OK' to proceed.

6. Place the OBJ File: Now, you can place the OBJ file in the AutoCAD drawing area by clicking on the desired location.

7. Adjust Position and Scale: Once the OBJ file is placed, you can further adjust its position and scale using the standard AutoCAD editing tools.

8. Save the Drawing: Finally, don't forget to save your AutoCAD drawing with the imported OBJ file.

That's it! You've successfully opened an OBJ file in AutoCAD and incorporated it into your design. With these simple steps, you can seamlessly work with OBJ files in AutoCAD for your 3D modeling projects.