Add how to use guide page

There is not a clear guide how to use this site. So, a how-to guide would be really useful. This should be updated regularly as the website still is in its development phase.

If you have any problem on using the site, then you can ask me, and I'll help you.

Start by surveying the repository for the existing site pages and any current documentation or usage instructions. Define the guide's coverage from the site's present functionality and verify that a newcomer can follow it to use the site. Done means a clearly accessible how-to guide exists and reflects the current development state.

Written by the indexing model from the issue text.