This Ruby example creates a vNIC profile.

# Find the root of the tree of services:
system_service = connection.system_service

# Find the network where you want to add the profile. There may be multiple
# networks with the same name (in different data centers, for example).
# Therefore, you must look up a specific network by name, in a specific data center.
dcs_service = system_service.data_centers_service
dc = dcs_service.list(search: 'name=mydc').first
networks = connection.follow_link(dc.networks)
network = networks.detect { |n| n.name == 'mynetwork' }

# Create the vNIC profile, with pass-through and port mirroring disabled:
profiles_service = system_service.vnic_profiles_service
profiles_service.add(
  OvirtSDK4::VnicProfile.new(
    name: 'myprofile',
    pass_through: {
      mode: OvirtSDK4::VnicPassThroughMode::DISABLED,
    },
    port_mirroring: false,
    network: {
      id: network.id
    }
  )
)

For more information, see http://www.rubydoc.info/gems/ovirt-engine-sdk/OvirtSDK4/VnicProfilesService:add.