Go to the Atlassian Marketplace page for JCreate and select Server from the drop-down on the rightJCreate
Buy or evaluate the add-on with a free 30-day trial
Enter the details on the new evaluation screen and generate a license
Download the jar file and log in to Jira to Confluence as an administrator
Click the Administration icon
Click Manage apps, Validate your credentials if needed
Click on and upload app to upload the jar file

The add-on is uninstalled from your Confluence instance.

In order to have more benefits from Jcreate:

you will need to install jcreate-widget-jira on your Jira instance

Show fields order as it is in Jira screens
Show screen tabs if exists in Jira
Show Jira system fields related description (for example, time tracking field description)

JCreate JCreate Supported Platforms:

...