So I have this Latitude 3340. It runs Windows 10 (build still undisclosed), and I have know idea where to start. It's currently running in "LEGACY BOOT: SECURE BOOT OFF".

I have an idea of what UEFI is, and apparently it's supposed to make boot time faster. The problem is, I don't know how to start.

Even though I'm a Microsoft developer, I don't know EVERYTHING about PCs, so how do I enable it?

If I do, will it make boot time considerably faster (I'm looking at <5 seconds, currently it's about 8-9)?

According to what I can find, it looks it definitely should speed up boot time.

How do I enable it? I click UEFI, and I see a whole bunch of boot files and folders...

It could be different in windows 10, but this should be how you do it in windows 8:
http://www.tomshardware.com/faq/id-1961933/configure-windows-ultra-fast-boot-uefi-gop.html