Clarify sections

README.md

@@ -1,12 +1,17 @@
 # Public releases for GitHub CLI
 
-## Homebrew tap
-
+## Install for Mac
+### Homebrew tap
+To install:
 ```sh
 brew install github/gh/gh
 ```
-
-## Debian/Ubuntu Linux
+To upgrade:
+```sh
+brew upgrade gh
+```
+## Install for Linux
+### Debian/Ubuntu Linux
 
 1. `sudo apt install git` if you don't already have git
 2. Download the `.deb` file from the [releases page](https://github.com/github/gh-cli/releases/latest)
@@ -14,14 +19,14 @@ brew install github/gh/gh
 
 _(Uninstall with `sudo apt remove gh`)_
 
-## Fedora/Centos Linux
+### Fedora/Centos Linux
 
 1. Download the `.rpm` file from the [releases page](https://github.com/github/gh-cli/releases/latest)
 2. `sudo yum localinstall gh_*_linux_amd64.rpm` install the downloaded file
 
 _(Uninstall with `sudo yum remove gh`)_
 
-## Other Linux
+### Other Linux
 
 1. Download the `_linux_amd64.tar.gz` file from the [releases page](https://github.com/github/gh-cli/releases/latest)
 2. `tar -xf gh_*_linux_amd64.tar.gz`
@@ -29,18 +34,24 @@ _(Uninstall with `sudo yum remove gh`)_
 
 _(Uninstall with `rm`)_
 
-
+## Usage
 ```console
 $ gh help
-Do things with GitHub from your terminal
+Work with GitHub from your terminal
 
 Usage:
-  gh [flags]
   gh [command]
 
 Available Commands:
   help        Help about any command
+  issue       Work with issues
   pr          Work with pull requests
+
+Flags:
+  -h, --help                    Help for gh
+  -R, --repo string             Select GitHub repository
+
+Use "gh [command] --help" for more information about a command.
 ```
 
 Thank you for trying out GitHub CLI! 🌟