Hello Phyllis!
To make system-wide changes to your MacBook, an administrator password is needed to approve the request. If this is your MacBook and you created the account when setting it up you are the administrative user. In the case, just enter the password you use to log into your MacBook.
If you received the MacBook through school, work, etc. you'd need the IT team there to approve of the changes. If you share the MacBook with someone else and they were the one who setup the MacBook, you'll need their account credentials to authorize the change.