If you are using the Windows operating system (you did not provide that information), and you are trying to install or update Flash Player, and you are in a Standard account (rather than an Administrator account); Windows will ask for the password of the Administrator account.
This request for the password is not coming from Adobe Flash Player. It is the Windows operating systems method of making sure only items that the computer owner wants to install are installed. It is a way to prevent hackers from installing software on your computer.
So, you will need to find the password for the Administrator account. When you find it put it somewhere safe where you can find it in the future.
The above info is my guess at what you are requesting.