Secrets are stored in 1Password, and so we need the 1Password CLI installed.
Start 1Password, configure account and then turn on integration with CLI (under settings->Developer)
NOTE: I have found that using the chezmoi install script means that the integration with the 1password-cli is broken. Using one of the packages (rpm, deb, macOS, Windows) seems to work fine though.
chezmoi init --apply stuartcampbell/dotfiles
Or to be a little more conservative:
chezmoi init stuartcampbell/dotfiles
Look at what changes would be applied
chezmoi diff
Now apply them
chezmoi apply -v