Edit .config/i3/config and add:

# change focus
bindsym $mod+h focus left
bindsym $mod+j focus down
bindsym $mod+k focus up
bindsym $mod+l focus right

# split in horizontal orientation
bindsym $mod+Shift+v split h

# split in vertical orientation
bindsym $mod+v split v

From https://faq.i3wm.org/question/2294/vim-and-keybinds.1.html