Perform the following steps to import an SSL certificate:

1. Open up a command window and go to the directory where the certificate file resides.
2. Generate a Java KeyStore (JKS) for Jira by running the keytool -genkey -alias jira -keyalg RSA -keystore $JIRA_HOME/jira.jks command.
3. Import the certificate into the KeyStore repository by running the keytool -import -alias jira -keystore $JIRA_HOME/jira.jks -file file.crt command, where file.crt is the certificate file.
4. Open the server.xml file located in the JIRA_INSTALL/conf directory in a text editor.

5. Locate and uncomment the following XML configuration snippet:

<Connector port="8443" 
maxHttpHeaderSize="8192" SSLEnabled="true" 
maxThreads="150" 
minSpareThreads="25" maxSpareThreads="75" 
enableLookups="false"
disableUploadTimeout="true" 
acceptCount="100" scheme="https" secure="true" 
clientAuth="false" 
sslProtocol="TLS" useBodyEncodingForURI="true"/>

6. Add a few new attributes to the Connector tag and save the file, as follows:

keystoreFile="PATH_TO_YOUR_KEYSTORE" 
keystorePass="PASSWORD_FOR_YOUR_KEYSTORE" 
keyAlias="jira" 
keystoreType="JKS" 

7. Restart Jira to apply the changes.