In order to create an aircraft, you must first be logged in as a client. As soon as you're logged in, you have to switch to the 'Aircraft' tab in the top right of the page.
Above the table with the already created aircrafts, there is the button 'New'. This button will open up an input mask, in which you can the aircraft data, the operation times, up to 4 cycles/counter, the owner of the aircraft, and e-mails, that get notified, when theres a change in the logbook.
With the 'Create' button you confirm your inputs and the aircraft gets created.