How do I create a work order from a ticket?

Open the ticket.
In the Work Orders section of the ticket sidebar, click Add.
Enter the Work Order Title and select the Work Order Type. Both are required.
Check the company, assets and parts, which are filled in from the ticket.
Create the work order.

You can create as many work orders as you need from one ticket. Each work order belongs to one ticket and shows a link back to it.

What is filled in from the ticket?

Company: if the ticket has a company, it is locked on the work order and cannot be changed. If the ticket has no company, you can choose one on the work order and it is applied to the ticket too.
Assets: in the creation form, you can change, remove or add assets. You can choose any asset from the ticket's company, not just the ticket's own assets. Once the work order is created, its assets cannot be changed.
Parts: you can unselect parts. The Parts field only appears if the work order type's form includes it. If assets are selected, only parts for those assets are available.

Once a company is assigned to the ticket or any of its work orders, it applies to the ticket and all of its work orders.

If any asset with no company is attached to the ticket or one of its work orders, no company can be assigned to any of them.

Ticket types are either internal or external. You can create internal or external work orders from both.
Sub work orders are not linked to the ticket.
Deleting a ticket does not delete its work orders.