Here's a simplified step-by-step guide to help you get started:

1. Open SolidWorks: Launch SolidWorks and create a new part file to begin your design.

2. Sketch the Flange: Use the sketch tools to create the profile of your flange coupling. This typically involves drawing circles for the bolt holes and a larger circle for the outer diameter of the flange. Make sure to dimension your sketch appropriately for accuracy.

3. Extrude the Sketch: Once your sketch is complete, use the Extrude feature to give your sketch depth and turn it into a 3D object. Specify the desired thickness for your flange.

4. Add Bolt Holes: Create sketches for the bolt holes on the flange. These are typically evenly spaced around the circumference of the flange. Ensure they are properly dimensioned and aligned.

5. Create the Shaft: Switch to a new sketch and draw the profile of the shaft that will connect to the flange coupling. This might be a simple circle or a more complex shape depending on your design requirements.

6. Extrude the Shaft: Similar to the flange, use the Extrude feature to give depth to your shaft sketch and turn it into a 3D object. Make sure the length matches the desired dimensions.

7. Combine Flange and Shaft: Utilize SolidWorks' assembly features to combine the flange and shaft into a single assembly. This involves positioning the flange and shaft correctly relative to each other.

8. Add Detailing: Fine-tune your design by adding any additional features or details necessary for your flange coupling, such as chamfers, fillets, or text annotations.

9. Review and Finalize: Take a moment to review your design, ensuring all dimensions are accurate and features are correctly positioned. Make any necessary adjustments.

10. Save and Document: Once satisfied with your design, save your SolidWorks file and consider creating detailed documentation or drawings to accompany your design for future reference.

Remember, this is a simplified guide, and there may be variations or additional steps depending on your specific design requirements. SolidWorks offers a plethora of tools and features to explore, so don't hesitate to experiment and learn as you go