How do I install a package globally?

[Trevor]

I'm just getting in to D , coming from a C and Python background. 
I've had a play with DUB and adding packages to my project, but 
it seems like there should be a way to install packages so they 
can be used in any D program I compile without creating a whole 
package. For example in Python you can just go "pip install abc" 
and then any script can use abc.

How does one install packages globally, and how can I write 
programs that use the third-party packages without being wrapped 
in a dub file?