[FLINK-15908][docs] Add description of support 'pip install' to 1.9.x documents.

docs/tutorials/python_table_api.md

@@ -31,10 +31,15 @@ to running a Python Table API program.
 
 ## Setting up a Python Project
 
-Firstly, you can fire up your favorite IDE and create a Python project and then
-you need to install the PyFlink package. Please
-see [Build PyFlink]({{ site.baseurl }}/flinkDev/building.html#build-pyflink)
-for more details about this.
+You can begin by creating a Python project and installing the PyFlink package.
+PyFlink is available via [PyPI](https://pypi.org/project/apache-flink/) and can be easily installed using `pip`.
+
+{% highlight bash %}
+# install the latest 1.9 version of PyFlink
+$ python -m pip install apache-flink==1.9.*
+{% endhighlight %}
+
+You can also build PyFlink from source by following the [development guide]({{ site.baseurl }}/flinkDev/building.html#build-pyflink).
 
 ## Writing a Flink Python Table API Program
 

docs/tutorials/python_table_api.zh.md

@@ -30,8 +30,15 @@ under the License.
 
 ## 创建一个Python Table API项目
 
-首先，你可以使用你最熟悉的IDE，创建一个Python项目。然后，你需要安装PyFlink包，
-请参考[构建PyFlink]({{ site.baseurl }}/zh/flinkDev/building.html#build-pyflink)了解详细信息。
+首先，使用您最熟悉的IDE创建一个Python项目，并且安装PyFlink。
+目前PyFlink已经上传至[PyPI](https://pypi.org/project/apache-flink/)，可通过`pip`安装：
+
+{% highlight bash %}
+# 安装PyFlink 1.9的最新版本
+$ python -m pip install apache-flink==1.9.*
+{% endhighlight %}
+
+如果您想从源码安装，请参考[构建PyFlink]({{ site.baseurl }}/zh/flinkDev/building.html#build-pyflink)了解详细信息。
 
 ## 编写一个Flink Python Table API程序