The parent describes how to do this with tmux right out of the box -- you don't need anything in your config to get this to work. Did you start tmux? If you haven't set up iTerm to connect to a tmux session by default, any new tabs/splits you make won't be running it. You should be able to tell by the presence of the status bar at the bottom.
I type `Ctrl+b [` and in top right it says [0/1] (even if i have a history of say 5 commands). when i press any vim knpfb keys the cursor doesn't do anything. I feel retarded
