Inventor ETO Server requires network licensing, so the first step is to set up a license server. The license server must be a different machine than ETO server will be installed on, and it cannot be a license server that is being used for standard network licensing. This is because Inventor ETO requires session specific licensing. See for details.
Select Network License Manager and press Install on the Configure Installation page and follow the instructions. Refer to the LicenseAdministration.pdf file located within the install directory of your Autodesk Network License Manager for more information.