I am new to nopCommerce and trying to make HTML to theme on it I googled lots of things but not able to get proper way to create customized theme nopCommerce, can any one help,<
A little help here: Overview (Designer's Guide)
The easiest way:
Copy the folder at ~/Themes/DarkOrange to ~/Themes/YOUR_THEME. Modify the corresponding items in theme.config.
If you need to change any view, copy that view from ~/Views/SUB_FOLDER/FILE_NAME.cshtml and paste it under ~/Themes/YOUR_THEME/SUB_FOLDER/FILE_NAME.cshtml.
For example, if you want to change the code in ~/Views/Shared/_ColumnsOne.cshtml, copy that file and paste it under ~/Themes/YOUR_THEME/Shared/_ColumnsOne.cshtml.
If you do not need to change any view, then modifying ~/Themes/YOUR_THEME/Content/styles.css is enough. (Also make sure you update ~/Themes/YOUR_THEME/Views/Shared/Head.cshtml to point to your CSS)
Rule of Thumb: nopCommerce will look for the specific view in your theme. If it can't find the view then it falls back to the original views at ~/Views. Otherwise your theme's views override the original views.
In addition to the Designers guide there are some nice articles describing why and how to use nopCommerce themes:
Why nopCommerce Theme?
How to create nopCommerce themes
Copy all the files inside ~/Views to your Themes: ~/Themes/YourTheme/Views
Then just modify any .cshtml file inside.
I hope it helps!