Canon EOS Rebel T4i 18-135mm IS STM Lens Kit Instruction Manual page 187

Adding to Existing Album
You cannot select an album shot with another camera.
Select [Add to existing album].
1
Follow step 4 on page 184 to select
[Add to existing album], then press
<0>.
Select an existing album.
2
Press the <U> key to select an
album, then press <0>.
Select [OK] on the dialog screen,
then press <0>.
Certain video snapshot settings will
change to match the existing album's
settings.
Press the <M> button to exit the
menu and return to the movie
shooting screen.
Shoot the video snapshot.
3
Go to "Creating a Video Snapshot
Album" (p.185).
3 Shooting Video Snapshots
187