To enable SSL you have to uncomment the given below mapping to enable SSL in server.xml file .
<!-- Define a SSL HTTP/1.1 Connector on port 8443 -->
<!--
<Connector port="8443" maxHttpHeaderSize="8192"
maxThreads="150" minSpareThreads="25" maxSpareThreads="75"
enableLookups="false" disableUploadTimeout="true"
acceptCount="100" scheme="https" secure="true"
clientAuth="false" sslProtocol="TLS" />
-->
Anwser of your second question that how to get certificate , to create a certificate you have to use keytool utility in
java to create a certificate and using jarsigner utility you have to sign your Application jar file.
Thanks