There are two ways shipments can be booked in for collection with DHL.
The first way is if you ship daily and have an arrangement with your DHL account manager and local operations, you will have a scheduled time where a delivery van will come to your warehouse and will pick up any shipments you have on your manifest. To arrange this type of collection you will need to contact your DHL account manager.
The second way is by requesting a collection from DHL when you are ready to ship. This can be done by calling local operators and requesting a collection as long as you have a prior agreement set-up.
For additional information about collection it would best to contact your DHL account manager.
If you need any clarification or help with anything else, get in contact with support.