2. i "cpanned" Geo::StreetAddress::US but now I don't know what to do. There is no example script.

CPAN module authors often tuck example scripts into their distributions. You just have to know where to look. From the Geo::StreetAddress::US link, click on the Geo-StreetAddress-US-0.99 link, then the MANIFEST link. There you will see 4 other links under a directory named 'eg' (which, I presume, is short for 'example'). manual_test.pl may give you a quick start.

I have no idea if this module does what you need. But, now you should have a little better idea how to navigate CPAN.

Is there a tutorial or documentation on how to utilize CPAN library functions for beginners anywhere?

Tutorials
Installing Modules
Using Modules

1. what is lmgtfy ?

Should be self-evident if your follow the link. Otherwise, google lmgtfy :)