How can I change the home currency in Quickbooks essentials after turn on multicurrency function?

You are only allowed to change the home currency before registering any transaction. You should open a new blank QBO account, enable the multi currency, and change the home currency.

https://quickbooks.grsm.io/Asia-Pacific

Then you may have 2 ways to migrate data from your old account:

1. Utilize a migration tool.

https://transactionpro.grsm.io/qbo

2. Purchase a 3rd party migration service.