To manually install the Securly SSL certificate

1. Download the Securly certificate CRT file.(Link)
2. Navigate to Finder > Applications > Utilities > Keychain Access
3. Select ‘System’ in the left-hand column.
4. Open ‘File > Import Items’ and import the ‘securly_SHA-256.crt’ files into the ‘System’ keychain.
5. The certificate should now show with a red X. That means it is untrusted. To provide trust, double-click the *.securly.com certificate. Under "Trust", change the setting at the top (When using this certificate) to "Always Trust".