Modify installation section.

README.md

@@ -52,8 +52,38 @@ MSI installers are available on the [releases page][].
 
 ### Other platforms
 
-Install a prebuilt binary from the [releases page][] or source compile by running `make` from the
-project directory.
+Install a prebuilt binary from the [releases page][]
+
+### Build from source
+
+1. Clone cli into `~/.githubcli`
+```
+$ git clone https://github.com/cli/cli.git ~/.githubcli
+```
+
+2. Compile
+```
+$ cd ~/.githubcli && make
+```
+
+3. Add `~/.githubcli/bin` to your $PATH for access to the gh command-line utility.
+
+  * For **bash**:
+  ~~~ bash
+  $ echo 'export PATH="$HOME/.githubcli/bin:$PATH"' >> ~/.bash_profile
+  ~~~
+  
+  * For **Zsh**:
+  ~~~ zsh
+  $ echo 'export PATH="$HOME/.githubcli/bin:$PATH"' >> ~/.zshrc
+  ~~~
+  
+  * For **Fish shell**:
+  ~~~ fish
+  $ set -Ux fish_user_paths $HOME/.githubcli/bin $fish_user_paths
+  ~~~
+
+4. Restart your shell so that PATH changes take effect.
 
 <!-- TODO eventually we'll have https://cli.github.com/manual -->
 [docs]: https://cli.github.io/cli/gh