1. Cook noodles: Boil the noodles in water until they're al dente. Drain and set aside.
2. Heat oil and sauté: Heat oil in a pan and sauté the diced onion, carrot, and capsicum until tender.
3. Add mixed vegetables: Add the mixed vegetables and cook until they're tender-crisp.
4. Add cooked noodles: Add the cooked noodles to the pan and stir-fry for 2-3 minutes.
5. Season: Add soy sauce or stir-fry sauce (if using) and season with salt and pepper to taste.
6. Serve: Serve hot and enjoy!