Upload your certs (yourCertificate.cert, yourPrivateKey.key, yourCA.crt) to your home folder
Logon to your Unifi controller via SSH
Run the following command to convert your certificate to a PKCS12 sudo openssl pkcs12 -export -in yourCertificate.cert -inkey yourPrivateKey.key -out yourNewCertName.p12 -name unifi -CAfile "yourCA.crt" -caname root -password pass:aircontrolenterprise
Copy your newly converted PKCS12 certificate sudo cp yourNewCertName.p12 /etc/ssl/private/
Bind your newly copied PKCS12 certificate to the Unifi services sudo keytool -importkeystore -deststorepass aircontrolenterprise -destkeypass aircontrolenterprise -destkeystore /usr/lib/unifi/data/keystore -srckeystore /etc/ssl/private/yourNewCertName.p12 -srcstoretype PKCS12 -srcstorepass aircontrolenterprise -alias unifi
Restart the Unifi services (or reboot your server) sudo /etc/init.d/unifi restart