[skip ci] Updated INSTALL.md. (#3016)

* Minor editorial updates.
Signed-off-by: NAmy Hong <yun.hong@zilliz.com>

* [skip ci] Updated INSTALL.md.
Signed-off-by: NAmy Hong <yun.hong@zilliz.com>

* [skip ci] Deleted "cd/home".
Signed-off-by: NAmy Hong <yun.hong@zilliz.com>

INSTALL.md

@@ -58,48 +58,35 @@ For GPU-enabled version, you will also need:
 
 ### Compilation
 
-#### Step 1 Install dependencies
+#### Step 1 Download Milvus source code
 
-##### Install in Ubuntu
+Download the latest Milvus source code and change directory:
 
 ```shell
-$ cd [Milvus root path]/core
-$ ./ubuntu_build_deps.sh
-```
-
-##### Install in CentOS
-
-```shell
-$ cd [Milvus root path]/core
-$ ./centos7_build_deps.sh
+$ git clone https://github.com/milvus-io/milvus
+$ cd ./milvus/core
 ```
 
-#### Step 2 Build
+#### Step 2 Install dependencies
 
-```shell
-$ cd [Milvus root path]/core
-$ ./build.sh -t Debug
-```
-
-or
+##### Install in Ubuntu
 
 ```shell
-$ ./build.sh -t Release
+$ ./ubuntu_build_deps.sh
 ```
 
-By default, it will build CPU-only version. To build GPU version, add `-g` option.
+##### Install in CentOS
 
 ```shell
-$ ./build.sh -g
+$ ./centos7_build_deps.sh
 ```
 
-If you want to know the complete build options, run the following command.
+#### Step 3 Build Milvus source code
 
 ```shell
-$./build.sh -h
+$ ./build.sh -t Debug
 ```
-
-When the build is completed, everything that you need in order to run Milvus will be installed under `[Milvus root path]/core/milvus`.
+When the build completes, everything that you need to run Milvus is under `[Milvus root path]/core/milvus`.
 
 ### Launch Milvus server
 
@@ -176,7 +163,6 @@ $ docker exec -it [container_id] bash
 Download latest Milvus source code:
 
 ```shell
-$ cd /home
 $ git clone https://github.com/milvus-io/milvus
 ```