Go to Sales Orders and select the orders that you want to create shipments for. Click "Bulk Actions", then select "Ship".
The following popup will appear:
Check or uncheck that box to decide if you want email notifications to be sent to your order recipients, then "Proceed".
If you wish to fulfil the order on Shopify, Select "NOTIFY CUSTOMER OF SHIPMENT - Send shipment details to your customer now" on Shopify, the order will sync to TradeGecko as Fulfilled but TradeGecko will not send a duplicate email notification of shipment to your recipients.