Same way as the larger part of other operating systems get infected. You trick people to install/run something. Mail with attachments, perhaps there's a vulner

Same way as the larger part of other operating systems get infected. You trick people to install/run something. Mail with attachments, perhaps there's a vulnerability in a pdf reader, openoffice, some media player to exploit perhaps the user will actually run that executable you sent. Download links with added malware. Drop a custom usb key and exploit the USB stack.