To get the Google Play Store on your Fire Tablet, you'll need to enable installations from unknown sources. This might sound sketchy, but trust me, it's worth it. Just go to your tablet's Settings, then Security, and toggle the switch to allow apps from unknown sources.
Next, you'll need to download the Google Play Store APK from a reputable website. I know, I know, it sounds like a hassle, but it's actually pretty straightforward. Just make sure you're downloading from a trusted source, or you might end up with some shady software on your hands.