Installation of Theme & Helper-Plugin

After downloading the full packages from ThemeForest you will get an zip folder named Houston.zip

Then Follow this process to install it inside your wordpress.
1.Goto Wp-Admin panel "Appearance > Themes"
2."Add new > Upload a theme"
3.Then Choose & Upload houston.zip file

After the installation of theme, there is a Admin-notice to install the Theme-Helper plugin and other required/recommended plugins.