themeforest can be an odd place to buy a plugin. It is a marketplace. You must double-check if the template factory is well-known and don't have bad reviews.
Top template factories frequently include these resources with a theme:
- The template, xxx-9.9.9-template.zip (version numbers are important)
- A quick-start or launcher, xxx-9.9.9-launcher.zip, this installer is an installable Joomla CMS, but it has been customized to match the demo site. It rarely includes the same demo images, but it has the same layout with boxes.
- Resources, related assets to create background, logos, etc.
- The framework, most well-known templates implement a framework to generate pages and configure settings. For example: Gantry, T3, Yoo, etc.
- Support Service. A site where you can ask pre-sales and support questions (so you don't have to ask here ;-) )
If the template provider does not provide these elements, (in my opinion) it is not a good template that will not be flexible. For example, it will have fixed colors or a static grid layout.
Ref: JWC15 - Why doesn’t my site look like the demo?!