Be sure to have a working OpenCart 2 installation before you attempt to install the theme.
1Copy theme files
Unzip the theme archive you have downloaded from ThemeForest. Upload all the files from OpenCart_v.2.x folder to the directory you have installed OpenCart in:
2OpenCart 2.0.x (skip this step for versions greater than 2.0.x)
In OpenCart admin panel go to Extensions › Extensions Installer and install the compatibility modification (patch) that can be found in Theme package > Additional.
Or you can delete
admin\controller\extension\module\folder and its contents.
3Theme (module) installation
In OpenCart admin panel go to Extensions › Modules or if you are using OpenCart 2.2+ Extensions > Themes and install the BurnEngine module.
In OpenCart admin panel go to System › Settings › Store Edit › Store › Template dropdown and choose BurnEngine
You can now check the First Steps section in order to find out how to install some sample data or adjust the theme settings to your needs.