AutoCAD is a widely used software for 2D and 3D design, and you may encounter situations where you need to import OBJ files for your projects. Here are the steps to open OBJ files in AutoCAD:

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

2. Access the 'Import' function: Once AutoCAD is open, go to the 'Insert' tab in the menu bar at the top of the screen.

3. Select 'Import': From the 'Insert' tab, click on the 'Import' option to open the import dialog box.

4. Choose OBJ file format: In the import dialog box, navigate to the location where your OBJ file is saved and select the file.

5. Set import options: After selecting the OBJ file, you may be prompted to choose import options such as scale, rotation, and insertion point. Adjust these settings according to your project requirements.

6. Confirm and import: Once you have set the import options, click 'OK' to confirm and import the OBJ file into your AutoCAD drawing.

7. Edit and work with the OBJ file: After importing the OBJ file, you can edit and work with it in your AutoCAD drawing. You can use AutoCAD's tools and features to manipulate the imported 3D model as needed.

8. Save your work: Once you have made the necessary changes to the imported OBJ file, remember to save your AutoCAD drawing to preserve your modifications.

By following these steps, you can successfully open and import OBJ files in AutoCAD to incorporate 3D models into your designs and drawings. This allows you to work with a variety of file formats and expand your creative possibilities in AutoCAD.