After you have purchased the theme, go to “Downloads” menu in your Themeforest account and download the theme package to your computer.
Extract it and find installable “secondtouch.zip” in the root folder of the theme package.
Log in your domain, where you have previously installed WordPress.
Go to Appearance>Themes>Add new>Upload theme and upload installable secondtouch.zip archive.
Activate the theme and begin installing and activating plugins.
If you want to import demo data, go to Appearance>Import demo data section and click “Import demo data” button.
After that don’t do anything. Simply wait till the import process is completed and you see “Import is completed” messages.
IMPORTANT NOTE! If you are going to customize theme files, we strongly recommend to install child theme at once. Child theme is located in “Child Theme” folder of theme archive.
More information about child theme you can find in this documentation article.