If you mean the master password to F-Secure Key, follow these instructions:
Note that if you forget the master password all data is lost
For Mobile Security I guess this time
You have to open a support ticket to get help with that: http://www.f-secure.com/en/web/home_global/support/contact/request
Or try resetting it from the "trusted number":
I moved your post to the more relevant board for Mobile security.
Please follow @NikK instructions above, so that we can help you with your problem.
Edit: Activated @mention notifications