To assign roles to users or groups in vCenter, you first need to navigate to the vSphere Client and select the object (such as a datacenter, cluster, or host) where the permissions will be applied.
After selecting the object, you use the 'Add Permission' option from the context menu to start the process of assigning permissions.
You then select the role you want to assign, which will be from the predefined list of roles in vCenter. These roles define the level of access for the user or group.