See this article Delete a keychain in Keychain Access on Mac - Apple Support
You can do in another way open keychain access with spotlight , select login ( be careful don't click on small Lock , as it will get locked and various pop will start appearing as it is open by default ) .
Jan 17, 2019 Here’s how the process looks: After pulling up Applications, find the app you’d like to change the icon for. Right click and select Get Info or use the keyboard shortcut command +.
Just right click on login and click on delete references .
Another method -
If keychain is prompting to enter password multiple times , & pop - up is not going away when safari is opened .
Mac Default Apps
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 .
Change Default App Macos
Open air port utility via spotlight > click on edit and enter your base station password .