User Accounts – Setting Administrator Privileges

I need to get administrator privileges from a user account. Launch osx seirra with version 10.12.6.
I have six accounts on my MacBook for me and my family. We are adminstrative the rest are for us. I also created an account in addition to the administrator account. I regularly use the user account. I have forgotten the password of the administrator account and we can not access it. Needless to say, this causes some problems here at home, we can still use our separate user accounts, but nothing that requires administrator privileges. An overview would be useful and appreciated.