I want to know how to install paid theme in magento 2.
I want a tutorial which show me all actions step by step.
Have you done the steps from the Magento dev docs? Ususally the way you can do it is the following
To install a theme manually:
Make sure that the directory structure you are copying is
<VendorName>/<theme>. And all the theme files are in the
Copy this directory to the /app/design/frontend directory.
Register a theme
After you create or install a theme, open the Magento Admin or reload any Magento Admin page. This way the theme gets registered and added to the database.
To make sure the theme is registered, in the Magento Admin navigate to Content > Design > Themes. If a theme is registered, it is displayed in the list of available themes.
Source: Dev Docs