Installing Creately diagramming plugin for Confluence is easy. This can be either done via the Universal Plugin Manager or manually.
You can automatically install the Creately plugin for Confluence through the Universal Plugin Manager. To install just go to Confluence Admin from the top right menu.
On the Confluence Administration page, select Manage Plugins from the Configuration menu on the left.
This will display the Plugins window. Select All available from the Plugins to show: drop-down menu, and search for 'Creately'.
Once Creately shows up, just select Creately and click on Free Trial to install and use the plugin.