I want to create VMs with more than only one NIC. But I cant figure out how to do this. When creating a new compute offering there is no option to add more NICs

--> Create Multiple networks and select multiple networks for the VM from the networks menu during the VM creation. A nic is created for each network associated with the VM.

if a user already created a VM there is no "Add NIC" button or something like that in the VM's NIC tab.

--> Currently this is not possible. This feature will be available in future releases, see the following link https://issues.apache.org/jira/browse/CLOUDSTACK-645

ok thanks, that solves my problem