Update FreeBSD section

Update FreeBSD section, including install / configuration / run / run as client.

README.md

@@ -59,6 +59,10 @@ sudo snap install shadowsocks-libev --edge
 - [Nix](#nix)
 - [Directly build and install on UNIX-like system](#linux)
 - [FreeBSD](#freebsd)
+    + [Install](#install)
+    + [Configuration](#configuration)
+    + [Run](#run)
+    + [Run as client](#run-as-client)
 - [OpenWRT](#openwrt)
 - [OS X](#os-x)
 - [Windows (MinGW)](#windows-mingw)
@@ -294,27 +298,49 @@ sudo make install
 You may need to manually install missing softwares.
 
 ### FreeBSD
+#### Install
+Shadowsocks-libev is available in FreeBSD Ports Collection. You can install it in either way, `pkg` or `ports`.
+
+**pkg (recommended)**
+
+```bash
+pkg install shadowsocks-libev
+```
+
+**ports**
 
 ```bash
-su
 cd /usr/ports/net/shadowsocks-libev
 make install
 ```
 
-Edit your config.json file. By default, it's located in /usr/local/etc/shadowsocks-libev.
+#### Configuration
+Edit your `config.json` file. By default, it's located in `/usr/local/etc/shadowsocks-libev`.
 
-To enable shadowsocks-libev, add the following rc variable to your /etc/rc.conf file:
+To enable shadowsocks-libev, add the following rc variable to your `/etc/rc.conf` file:
 
 ```
 shadowsocks_libev_enable="YES"
 ```
 
+#### Run
+
 Start the Shadowsocks server:
 
 ```bash
 service shadowsocks_libev start
 ```
 
+#### Run as client
+By default, shadowsocks-libev is running as a server in FreeBSD. If you would like to start shadowsocks-libev in client mode, you can modify the rc script (`/usr/local/etc/rc.d/shadowsocks_libev`) manually.
+
+```
+# modify the following line from "ss-server" to "ss-local"
+command="/usr/local/bin/ss-local"
+```
+
+Note that is simply a workaround, each time you upgrade the port your changes will be overwritten by the new version.
+
 ### OpenWRT
 
 The OpenWRT project is maintained here: