To sync across all your existing registered customers, you can use the Bulk Sync module in eWI Core.
Head over to your Plugins list on your wp-admin section and click the ‘Bulk Sync’ link under the ‘Woocommerce Intercom Integration’ plugin.
Note: This will only sync across returning customers or those who registered at checkout.
Note: It will sync across their customer data and their Total Spend and Number of Orders, to tag them with purchased orders or active subscriptions, please check out the Bulk Sync Tags addon.