@Innocent Heartvoice , Thanks for posting in Q&A.
To set up co-management, there are two ways. One is for existing configuration manager managed devices quickly enrolled into Intune.. The other is for the device first enrolled with Intune. They are cloud-first devices and use Intune to install the Configuration Manager client. Here is a link with more details:
After the device is co-managed, then we will consider switch the workload you want to Intune. If you want some workloads keeps in Configuration Manage, you can leave it there. For example, you can leave the Windows update policies on Configuration Manager. To know more about co-management workloads, you can read the following link:
For the licensing for co-management, here is link with some scenarios guide you how to choose license. You can read it as a reference:
Hope it can help.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.