Please follow these steps:
Backup wp-content directory and all other important files inside your WordPress installation.
Also, backup your website database (this option should be available in your hosting account management panel).
You need to tell visitors that the website is under maintenance at the moment. Create a file ”.maintenance” in the root directory of WordPress. This will show “maintenance” message to your visitors instead of the website pages. Put the following content in it:
$upgrading = time();
Make sure that you didn’t modify files in these directories:
If you did change files in the above directories, please backup those files. You will need to merge your changes into the updated files after update.
Please make sure that you have backed up your WordPress database and files before you proceed. Please refer to step 1.
Remove the following plugins’ folders:
Extract the plugins from the zip archives in the “Plugins” directory of the theme download. Extract the theme folder from the business-idea-wp.zip file in the root directory of the theme download. Replace the plugins and the theme folders from the list above with the plugins and theme folders you’ve just extracted (for example, the extracted business-idea theme folder should replace the wp-content/themes/business-idea folder on the server).
Delete ”.maintenance” file that you created in step 2.