Both buyers and suppliers can place Trade Assurance orders.
If you have found an online product on Alibaba.com:
You could click “Start Order” on product detail page to place prder directly or click “Contact supplier” to check more details with the supplier, then ask supplier to draft the order for you.
If you want to draft order directly for customized products:
You could click “Order with Trade Assurance” on the Alibaba.com homepage to draft an order or go to “Orders” > “All Orders” and click “Draft Trade Assurance Order“. 
Then choose to “add products” or “add contract” directly.
After submitting the order, you could manage your order on Order Management page.