In this case, the eazier way to propose all delivery methods to your client is to use our frontend. This is Javascript based and can be integrated very quickly. More info on how to integrate it here
You can obviously create your own map etc. using our GOE6 API which requires more development and bring less more flexibility.
When the order is created, you can get its labels via a simple API Call: [Create Label]. See how it work in the section C.3 Shipping Manager API of our integration manual.
In all cases, we highly advice you to have a look at our article that gives you an overview of the different possibilities to make an integration with our systems:
If you have built a plugin and want to share it with us please send us an email to esolutions@bpost.be, we will be pleased to communicate officialy and promote it.