How to use burst / slow-mo features on Nexus 6p?

This is for Google Camera v3.0 and up:

Video

Open Google Camera app

Swipe from right to left for Video mode.

In the top right, touch the icons to turn features on or off:

Slow motion: Set slow motion to 120 fps or turn off slow motion.

Note: On Nexus 6P devices, there's an option for 240 fps. 240 fps produces a higher quality slow motion video than 120 fps, but requires more storage space on your device.

Flash: Turn flash on or off, or set to auto (for auto, you'll see an "A" in the icon).

Photo

You can choose what Google Camera does with your photo bursts. There are two settings you can turn on or off:

“SmartBurst”: Automatically save only the best photos in a burst.

“Auto-generate creations”: Automatically turn your photo burst into an animation or collage.

To turn these settings on or off:

Open Google Camera app.

At the top left, touch Menu > Settings > Burst settings.

Next to each setting, touch the switch to turn the it on or off.

For full details see:
See: https://support.google.com/googlecamera/#6306661