Well you can't. Only the Windows version has a built in License manager and that allows to just have it as a download. For other platforms you can only download limited evalution versions. For the real version you have to contact NI to get a media with the software on it. If you have an active MSP for that version you will get that media automatically.
not sure it is even there for Linux. They don't build a new evalution version for every LabVIEW release for Linux. If it is available it's likely on the ftp site somewhere.
As far as I know there is no download for the Linux version of LabVIEW. You can try signing up for the Beta, although I'm not sure you can still get in this year or not. The best way is probably to contact your local sales rep and have a chat. No guarantee you'll be able to get a free trial. But it's probably worth asking.