If your are on Chrome:
Click the triple-dotted icon at the top-right corner, and go to "settings".
Type "certificate" into the BLUE search bar at the top.
Click "security" from the list.
Scroll all the way to the bottom of the page, and click "Manage certificates"
Click "authorities", and then click "import". Select the downloaded file from the new folder which you have moved it into.
Keep clicking "next" until it is installed.
Once installed, restart the browser.
If your are on Firefox:
Go to settings and search "certificate".
Click "View Certificates" button.
Select "Authorities" and then click "Import". Select the downloaded file from the new folder which you have moved it into.
Keep clicking "next" until it is installed.
Once installed, restart the browser.
If your are on Safari:
Follow these instructions to install the file that you have downloaded earlier:
https://support.apple.com/en-sg/guide/keychain-access/kyca2431/mac
Once installed, restart the browser.