Alexander,
First, you have to login using your AkeebaBackup.com account. It's the same one you use on the forum.
Then, go to the top menu Professional Services -> My Downloads. In the new page, click on the "Akeeba Backup 3.0 Alpha" folder. A new page will load and you will see the ZIP file. Click on the download icon towards the right end of the page. The file will download under a mangled name (something like abcdef01234.zip). This is normal. Use this ZIP file to install Akeeba Backup Professional on your site.
Nicholas K. Dionysopoulos
Lead Developer and Director
π¬π·Greek: native π¬π§English: excellent π«π·French: basic β’ π My time zone is Europe / Athens
Please keep in mind my timezone and cultural differences when reading my replies. Thank you!