Signing APK?

I just purchased the PRO version for one year (wanting/hoping to publish to Google Play Store).
I generated the APK.
Now onto the signing APK step it says i need to do it on a compatible Apple Macintosh but I am using a Windows PC.
Can somebody please walk me through what i need to install/do in order to sign my APK?
I see APK signer in my GS Creator->Tools menu and I filled out as much info as i can but I don't know where to browse too for the 4 red fields that require me to browse to some files.
Thanks in advance.