Since devs (devops, whatever) are often tasked with doing this, when a sysadmin is not there, here is a good short tutorial what to do with a crt file to get it working with wildfly:
http://reallifejava.com/configuring-ssl-in-wildfly-8/
TLDR
1) create a p12 from the crt file e.g.
openssl pkcs12 -export -in ServerCertificate.crt -inkey yourdomain.com.key -out yourdomain.com.p12 -name default -CAfile CertificateBundle2.crt -caname root
2) import the p12 you created into java keystore
keytool -importkeystore -deststorepass <secret password> -destkeypass <secret password> -destkeystore yourdomain.com.jks -srckeystore yourdomain.com.p12 -srcstoretype PKCS12 -srcstorepass <secret password used in csr> -alias default
3) reference keystore in standalone.xml
<security-realm name="SslRealm">
<server-identities>
<ssl>
<keystore path="yourdomain.com.jks" relative-to="jboss.server.config.dir" keystore-password="<secret password>"/>
</ssl>
</server-identities>
4) add listener with the https socket binding using this security realm
<https-listener name="default-ssl" socket-binding="https" security-realm="SslRealm"/>
see also: