Way to improve web pages

For Google, they have clear guidelines to follow and optimize the pages. They provide easy guide and testing results.
Take a look at this link for more details, https://support.google.com/webmasters/answer/40349?hl=en

Sorry for that I need some detailed notes to do the improvements.

Lucas,
how to ensure the sitemap generated, is good enough for the Crawler?

how to submit the sitemap file to Google, Yahoo and Bing?

You will submit the sitemap inside of your Webmaster Tools (WT) account. WT will tell you if the sitemap is valid and if your pages are being indexed.

Bing also has a webmaster tools platform.

Once you submit your sitemap to Google and Bing webmaster tools, your site will be indexed by both engines unless there is an error.

Thanks Lucas.
where can I submit sitemap, respectively, to Google, Yahoo and Bing?

You have to be logged into Webmaster Tools in order to submit a sitemap. Here is how to do it in Google and Bing(Yahoo).

Thanks a lot. I did ever submit sitemap to Google, like
https://www.google.com/webmasters/tools/home?hl=zh-TW

but I don't know why I can't easily get the web-site url, from google.

Webmaster tools will show you if the site is indexed. Also, you can type this into the Google search bar to see the same info:

site:yourdomainname.com

Hi,
I do not know how to improve the search, to be able to quickly locate to

http://my-friend.co/Start

within Google search, by typing anything like

Make friend

You can see this single page in Google here:
https://www.google.com/search?q=site%3Amy-friend.co

The site is indexed.

However, if you want the site to show up for "make friend" you will need to create content about 'making friends'. Currently the site doesn't have any visible content except for a single background image and the following text on the homepage:

[quote]Are you still on the way to seek your 2nd half there?

This site can be the place for you to find her/him out![/quote]

To rank well for 'making friends' you will need to create interesting content about this subject and optimize your site around it.

I have already adjusted the words on the web-page to be

Make New Friend

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but how can I ensure that I can find out the url, within Google/Bing/Yahoo, by only typing "Make New Friend"?

Page title and meta-title usually give good result.

The domain name itself let say makenewfriend.com have good chance to appear first.

You can add  noodp, noydir  to prevent displaying the wrong site description, this can make a difference...
<meta name="robots" content="index, follow, noodp, noydir">

Thanks. I've already added these

    ...
        <meta name="robots" content="index, follow, noodp, noydir">
    <title>Make Friend</title>

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to the deployed page. why still can't I search it out, on Google?

The problem is that your site have only one page and no content on it.
Google will index site with content otherwise your site will be considered as poor content and will not be well indexed maybe not indexed at all. Google scan the content of the page if it see nothing, your site will be ignored.

Add content that explain the website with good keywords, add about page, contact us page that will help to get some credibilities.

Who will register, if there is no information?

Other than about page and contact us, is there other information to show?

And there is "Support" to point to relevant contact information as well, on the page. Is that helpful and why can't the home page be located well, on Google, by putting "Make friend"?