Tomcat is the right choice.
This command generates the private key "keytool -keysize 2048 -genkey -alias tomcat -keyalg RSA -keystore tomcat.keystore"
This command generates the CSR which you need to send to Go Daddy "keytool -certreq -alias tomcat -file csr.txt -keystore tomcat.keystore"
Judging from the screenshot, it looks like you have a certificate and a key. Can you tell us what you find in /opt/vmware/horizon/workspace/logs/configurator.log when you see this error on the UI