In order to be able to send insured shipments with Aramex, you will need to register for the Aramex SHIELD service. More information about this can be found on the Aramex website, here: https://www.aramex.com/shield
Once you have registered for SHIELD, simply select the Insurance enhancement when booking your Aranex shipment in Shiptheory.
If you have any other questions, just get in contact with our support team.