You can start your trip by visiting tirthan valley near kullu, it's the most peaceful place in Himachal, explore there for 2 days.
After that you can head to Manali, go for bhrigu lake trek, Solange valley or Himalayan park, it depends on to take 2-3 days in manali.
Now you have 2 days left, you can head either to Parvati valley or Shimla.
This completes your journey.
Hey! If you want to visit a less crowded place in Himachal go for Jibhi, jalori pas (3 days). You can also visit Teerthan valley and Kulli. In 5-6 days. If you want you can visit my profile to read about trip to Jibhi jalori.