Follow below steps to insert vault key and password.
- To enable the AdminServices in esb set the HideAdminServiceWSDLs property to false in carbon.xml located in <ESB_HOME/repository/conf/carbon.xml.
<HideAdminServiceWSDLs>false</HideAdminServiceWSDLs>
- Restart the server to take effect of the configuration changes.
- Create SOAPUI project using the below WSDLs (make sure to change the host name port as per your environment. Here default environment settings are used)
https://localhost:9443/services/PropertiesAdminService?wsdl https://localhost:9443/services/MediationSecurityAdminService?wsdl
- The SOAP projects will look like below.

- First invoke the MediationSecurityAdminService AdminService to get the encrypted value. Please use basic authentication when invoking the AdminServices. Use the doEncrypt method as below.

- Now invoke the PropertiesAdminService AdminService. Use the “SetProperty” method as below:
<ser:path> (Registry location) uses the /_system/config/repoitory/components/secure-vault (always this is the path for this element) <ser:name> - Vault key <ser:value> - encrypted value (this value received from the above doEncrypt method).

- After adding this, you are able to check the password using “wso2:vault-lookup('shadsha12')” xpath expression. Following is sample proxy configuration that is used to check this scenario.
<?xml version="1.0" encoding="UTF-8"?> <proxy xmlns="http://ws.apache.org/ns/synapse" name="testProxy" transports="https,http" statistics="disable" trace="disable" startOnLoad="true"> <target> <inSequence> <log level="custom"> <property name="new_Password" expression="wso2:vault-lookup('shadsha12')"/> </log> <drop/> </inSequence> </target> <description/> </proxy
- Received below results when invoking the above service.

Please refer [1] for more information on "Calling Admin Services from Apps".
[1] https://docs.wso2.com/display/ESB481/Calling+Admin+Services+from+Apps