Hi Grace,
Last I checked, the Auctiva Insurance was only available for members in US and Canada (as point of package origin). If you're not resident in either or shipping from either, your best bet is use of your shipper's insurance. The FAQ at the HELP link (top of page), has a section on the Insurance Plan with many details that might help.
Normally, the seller always purchases any required insurance for the buyer, as part of the transaction. The Auctiva Insurance plan is simply used in place of Shipper's Insurance (like US Postal Service Insurance) and not added as second insurance. The buyer pays you for shipping and (optional) insurance for an item at checkout. If you are enrolled in the plan, you can automatically buy the insurance for shipping. The insurance is billed to you by Auctiva for your account.
As example......
I normally ship everything using the US Postal Service. When insurance is needed on a transaction, it's detected by Auctiva during checkout and billed to my account. Buyer is notified automatically of the insurance coverage by Auctiva. I ship the item as usual with USPS shipping (I use PayPal Click-n-Ship), but don't pay for any USPS insurance. Auctiva sends me a bill at the end of the month, which I pay separately with PayPal (one bill for all insurance purchased that month).
Hope that makes sense and helps explain how it works.
Danno