diff --git a/USAGE.md b/USAGE.md
index 2c0e3656..4cfb2c35 100644
--- a/USAGE.md
+++ b/USAGE.md
@@ -1,5 +1,12 @@
 # How to write documents with Markdown
 
+## Required Python modules
+
+* markdown
+* markdown_checklist
+
+## Usage
+
 * Organize articles in directories, each directory is a chapter.
 * Order of chapters is hard-coded in file `convert.sh` (parameter
   `all_chapter_dirs`), so that we can avoid complex/unnecessary way to order them.
@@ -8,42 +15,50 @@
 * Additional links stored in file `_links.md` will be appended to chapter.
 
 ```
-|- <language>/
-    |- _lang.md: Full name of the language. REQUIRED. e.g. `English` for `en_US`.
+|- <language>/              # Short language code. e.g. `en_US`. Required.
+    |- _lang.md             # Full name of the language. REQUIRED. e.g. `English` for `en_US`.
     |- chapter_name_1/
-        |- _title.md: Chapter title. REQUIRED
-        |- _links.md: Additional links, will be appended to chapter. OPTIONAL
-        |- _summary.md: Summary text of this chapter, will be displayed under
-                        chapter title. OPTIONAL
-        |- what_is_iredmail.md
-        |- why_choose_iredmail.md
+        |- _title.md        # Chapter title. REQUIRED
+        |- _links.md        # Additional links, will be appended to chapter. OPTIONAL
+        |- _summary.md      # Summary text of this chapter, will be displayed
+                            # under chapter title. OPTIONAL
+        |- article-1.md
+        |- article-2.md
+        |- article-3.md
     |- chapter_name_2/
         |- ...
     |- chapter_name_3/
         |- ...
     |- ...
-- html/css/markdown.css
-- html/images/
+
+- html/css/markdown.css     # CSS file
+- html/images/              # Place images you need to display in HTML files here
 ```
 
 * Articles will be ordered automatically, if you want to specify the order,
   prepend a digit number and `-` in article files, script `convert.sh` will
   remove this prefix during converting Markdown source file to HTML file. e.g.
-* The first line in article file will be used as article title. Note: it must
-  be the first line in file, not the first non-empty line.
+  `1-file1.md`, `2-file2.md`.
+* If you don't want to show an article in index page, prepend `0-` in its
+  file name as shown above.
 
 ```
 - chapter_name_x/
     |- _title.md
-    |- 1-what_is_iredmail.md
-    |- 2-why_choose_iredmail.md
-    |- 3-price.md
+    |- 1-article-a.md       # This article will be displayed as first one on index page
+    |- 2-article-b.md       # 2nd article on index page
+    |- 3-article-c.md       # 3rd article on index page
     ...
-    |- 0-hidden_article.md
+    |- 0-hidden_article.md  # This article will not be displayed on index page
 ```
 
-* If you don't want to show an article in index page, prepend `0-` in its
-  file name as shown above.
+* The first line in article file will be used as article title (string `# `
+  at beginning of line will be removed). Note: it must be the first line in
+  file, not the first non-empty line. For example:
+
+```
+# This is article title.
+```
 
 * Run script `convert.sh` to convert Markdown files to HTML static files.
 
@@ -60,8 +75,3 @@ To recompile all files, append flag `--all`:
 ```bash
 $ bash convert.sh --all
 ```
-
-## Required Python modules
-
-* markdown
-* markdown_checklist