Canon EOS 6D Instruction Manual page 198

Using AF to Focus (AF Method)
You cannot take a picture during autofocusing. Take the picture while the
Live View image is displayed.
198
3
Focus the subject.
Aim the AF point over the subject and
press the shutter button halfway.
The Live View image will turn off, the
reflex mirror will go back down, and
AF will be executed. (No picture is
taken.)
When focus is achieved, the beeper
will sound and the Live View image
will reappear.
The AF point used to focus will light
up in green.
If focus is not achieved, the AF point
will blink in orange.
4
Take the picture.
Check the focus and exposure, then
press the shutter button completely to
take the picture (p.180).