Not understanding the quick start step

I installed the docker toolbox and ran with that, but when I tried to type in

docker build -t bc/cert-issuer:1.0

it says
$ docker build -t bc/cert-issuer:1.0
"docker build" requires exactly 1 argument.
See ‘docker build --help’.

Usage: docker build [OPTIONS] PATH | URL | - [flags]

Build an image from a Dockerfile

I’m not sure what else I should be doing as I am in the folder where cert-issuer is installed

whoops I forgot the dot.