Hi usuarioITgen and welcome to the community!
While this question is not VMware related it will help to answer it for people trying to license guests in this environment
First you need to ensure you have Windows DataCenter licenses for every core in the ESXi in the cluster.
You don’t enter this anywhere in VMware unless you are using templates to deploy VMs in which you can enter the MAK in the Customisation Spec (https://docs.vmware.com/en/VMware-vSphere/6.5/com.vmware.vsphere.vm_admin.doc/GUID-CAEB6A70-D1CF-446E-BC64-EC42CDB47117.html). Otherwise you enter the MAK inside the Windows OS once you have built it so that you can activate the license against Microsoft.
Another option is to use a KMS which means that you don’t need to enter the key in the guest OS and they activate against the KMS (or AD if using Windows 2016 and AD-based activation).
The KMS key is a different one than the MAK but should be in your portal as well.
Dont worry about the activation count. You can get this easily extended by Microsoft. There is a token number given so as long as you have licensed every core on every ESXi host then you can deploy away.
Does that make sense?