diff --git a/HomebrewFormula/mkcert.rb b/HomebrewFormula/mkcert.rb
new file mode 100644
index 0000000..f1be4f8
--- /dev/null
+++ b/HomebrewFormula/mkcert.rb
@@ -0,0 +1,18 @@
+class Mkcert < Formula
+  desc "Simple tool to make locally-trusted development certificates"
+  homepage "https://github.com/FiloSottile/mkcert"
+  head "https://github.com/FiloSottile/mkcert.git"
+
+  depends_on "go" => :build
+
+  def install
+    ENV["GOPATH"] = buildpath
+    mkcertpath = buildpath/"src/github.com/FiloSottile/mkcert"
+    mkcertpath.install buildpath.children
+    cd mkcertpath do
+      system "go", "build", "-o", bin/"mkcert"
+      prefix.install_metafiles
+    end
+  end
+end
+  
\ No newline at end of file
diff --git a/README.md b/README.md
index 7823db0..8ffa3ab 100644
--- a/README.md
+++ b/README.md
@@ -20,18 +20,18 @@ Created a new certificate valid for the following names 📜
 The certificate is at "./example.com+4.pem" and the key at "./example.com+4-key.pem" ✅
 ```
 
-![Chrome screenshot](https://user-images.githubusercontent.com/1225294/41887838-7acd55ca-78d0-11e8-8a81-139a54faaf87.png)
+<p align="center"><img width="444" alt="Chrome screenshot" src="https://user-images.githubusercontent.com/1225294/41887838-7acd55ca-78d0-11e8-8a81-139a54faaf87.png"></p>
 
-Obtaining certificates from real CAs for development can be dangerous or impossible (for hosts like `localhost` or `127.0.0.1`), but self-signed certificates cause trust errors. Managing your own CA is the best solution, but usually involves arcane commands, specialized knowledge and manual steps.
+Using certificates from real CAs for development can be dangerous or impossible (for hosts like `localhost` or `127.0.0.1`), but self-signed certificates cause trust errors. Managing your own CA is the best solution, but usually involves arcane commands, specialized knowledge and manual steps.
 
-mkcert automatically creates and installs a local CA in the system root store, and generates locally-trusted certificates for any hosts.
+mkcert automatically creates and installs a local CA in the system root store, and generates locally-trusted certificates.
 
 ## Installation
 
 On macOS, use Homebrew.
 
 ```
-TODO
+brew install --HEAD FiloSottile/mkcert/mkcert
 ```
 
 On Linux, use [the pre-built binaries](https://github.com/FiloSottile/mkcert/releases), or build from source.
diff --git a/main.go b/main.go
index 27435d7..5bdec6e 100644
--- a/main.go
+++ b/main.go
@@ -81,7 +81,23 @@ func (m *mkcert) Run(args []string) {
 	}
 
 	if len(args) == 0 {
-		log.Println("Usage: TODO")
+		log.Printf(`
+Usage:
+
+	$ mkcert -install
+	Install the local CA in the system trust store.
+
+	$ mkcert example.org
+	Generate "example.org.pem" and "example.org-key.pem".
+
+	$ mkcert example.com myapp.dev localhost 127.0.0.1 ::1
+	Generate "example.com+4.pem" and "example.com+4-key.pem".
+
+	$ mkcert -uninstall
+	Unnstall the local CA (but do not delete it).
+
+Change the CA certificate and key storage location by setting $CAROOT.
+`)
 		return
 	}