a. Go to ECAS site of the EU and register yourself (as a person, not the organisation). You will get a confirmation email and it has a temporarily password that expires after 24 hours. Now you are registered at European Commission's Authentication Service (ECAS).
b. Then, go to portal of the Erasmus+ programme. If you are still logged in at ECAS, you are automatically logged in here as well. Otherwise, use the same log in details as ECAS. Click organisations and a drop down menu appears. Select register and fill in the details. It will ask you to upload some legal things (like registration papers, chamber of commerce, and such alike) but that you can also add/ upload later, after the deadline, as it is not part of the application procedure itself.