Rhino is a powerful 3D modeling software that allows you to create stunning designs and structures. If you have an OBJ file that you want to open in Rhino, it's a fairly straightforward process.

Here's how you can do it:

1. Open Rhino: First, launch Rhino on your computer. If you don't have it installed, you can download it from the official Rhino website.

2. Import OBJ File: Once Rhino is open, go to the 'File' menu and select 'Import'. Navigate to the location where your OBJ file is saved and choose the file you want to import. Click 'Open' to import the OBJ file into Rhino.

3. Adjust Settings: Depending on the size and complexity of the OBJ file, Rhino may prompt you to adjust import settings such as the unit system, scale factor, and vertex welding tolerance. Make any necessary adjustments and click 'OK' to proceed.

4. Start Modeling: Once the OBJ file is successfully imported, you can start working with the 3D model in Rhino. You can make edits, apply textures, and incorporate the OBJ file into your larger design project.

5. Save Your Work: After you've made your changes to the OBJ file, don't forget to save your work in Rhino. Go to the 'File' menu and select 'Save' or 'Save As' to save the modified 3D model in Rhino's native file format.

By following these simple steps, you can easily open an OBJ file in Rhino and leverage its powerful 3D modeling tools for your design projects. Whether you're a professional designer or a hobbyist, Rhino provides the tools you need to bring your 3D creations to life.