Updating files ...

I just recently did the full install of v1.3.9a on my local host to setup my store before I go live. Now there's the new updates which I'm confused on how to go about updating. Do I use the new installer and specify the same data as I did to install v1.3.9a or can I simply "drag" copy and paste the new files in v1.3.9b to the relative folder in my shop v1.3.9a to override ? or is there more than that to it ?

This statement I read below but it doesn't really explain:

"If you're upgrading from v1.3.9a, you can simply update the files listed in the "Changelog for v1.3.9b" in the /docs/ folder of the download zip."

Thank You

"If you're upgrading from v1.3.9a, you can simply update the files listed in the "Changelog for v1.3.9b" in the /docs/ folder of the download zip."
As it states....
Download and unpack them on your local
View the changelog and transfer those files to your install