Drop Zabbix Graph macro on a page and specify Server, Host and Graph parameters. You may also set the Period (in seconds), Width and Height of the graph in pixels.
Save the page and you will see the selected Zabbix graph:
You can put as many Zabbix graphs on a Confluence page as you need.
You may share you Zabbix graph with unauthenticated users as described in Zabbix Plugin Setup.