From the information you provided us, I saw that HTTPS protocol is used. In this case, SSL certificate needs to be imported to JAVA keystore. This could be done by using keytool. The syntax is the following:
keytool -importcert -alias <certificate_alias> -file <certificate> -keystore <target_keystore>
<certificate> is the path to the .crt file
<target_keystore> is java keystore by default located in
Keytool will first ask for a password of the keystore, which is “changeit”. Then it will show information about the certificate and ask you for approval, you need to click “yes”.