Canon EOS Rebel T3 18-55mm IS II Kit Instruction Manual page 134

Changing the Autofocus Mode
You cannot take a picture during autofocusing. Take the picture while the
Live View image is displayed.
134
Focus the subject.
3
Aim the AF points 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.
When focus is achieved, the AF point
which achieved focus will turn green
and the Live View image will
reappear.
If focus is not achieved, the AF point
will turn orange and blink.
Take the picture.
4
Check the focus and exposure, then
press the shutter button completely to
take the picture (p.122).