Login passwords are stored as a memory in user library > keychain folder .
If there are pop ups appearing on mac and not deleting even you enter correct admin password is due to login password do not match keychain access password ( as per theory both are kept as same ) .
This method works for El Capitan and older versions " Only " , for Mac OS Sierra and Mac OS High Sierra there are various methods ( like recovery mode ) or using apple articles or deleting login keychain adding a new keychain etc .
You can read this method .
If keychain is prompting to enter password multiple times , & pop - up is not going away when safari is opened .
Click on Go > Go to folder & type ~/Library then find a folder > keychains > remove first folder ( alfa numeric folder ) to trash . Restart & empty the trash , open system preferences go to internet accounts & once again configure web mail account , I cloud mail account by entering their passwords .This is applicable in Mac OS X El - Capitan and previous versions .
Open air port utility via spotlight > click on edit and enter your base station password .