If you have an Android with the Google Keyboard (Gkeyboard) as the main keyboard, you don't need to install our keyboard. The emojis will be available in your actual keyboard.
If you haven't the GBoard, You need to install our keyboard if you want to share the emojis fast and directly. Some platforms works really good with custom keyboards like facebook or ig.
But, you always can download the emojis in your gallery and attach them like a photo.