Are you looking to incorporate 3D models from OBJ files into your Revit design projects? Here's a simple guide to help you open OBJ files in Revit.

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

2. Open a New or Existing Project: Choose whether you want to open an existing project or create a new one where you intend to import the OBJ file.

3. Go to the Add-Ins Tab: Once your project is open, navigate to the Add-Ins tab on the ribbon.

4. Click on 'External Tools': In the Add-Ins tab, look for the 'External Tools' button and click on it.

5. Select 'OBJ File Importer': A dropdown menu will appear when you click on 'External Tools'. Look for the option that says 'OBJ File Importer' and click on it.

6. Choose the OBJ File: A dialog box will open, prompting you to select the OBJ file you want to import. Navigate to the location of your OBJ file, select it, and click 'Open'.

7. Adjust Import Settings: Depending on the OBJ file, you may need to adjust the import settings such as units, scale, and positioning. Ensure that the settings are appropriate for your project requirements.

8. Import the OBJ File: Once you've configured the import settings, click 'Import' to bring the OBJ file into your Revit project.

9. Place the 3D Model: After importing the OBJ file, you can place the 3D model within your Revit project by clicking to define its position.

10. Modify and Integrate: You can now modify the 3D model as needed and integrate it into your design project, taking advantage of Revit's powerful tools for architectural, structural, and MEP design.

By following these steps, you can seamlessly open and import OBJ files into Revit, making it easier to incorporate 3D models into your architectural and engineering projects. Whether you're working on a new building design, renovation, or retrofitting project, leveraging 3D models can enhance your visualization and collaboration efforts within Revit.