To install an imithemes’s theme you must have a latest version of WordPress already installed. For information in regard to installing the WordPress platform, please see the WordPress Codex –http://codex.wordpress.org/Installing_WordPress
Step 1: Download the installable theme from your Themeforest/Codecanyon Downloads page, you will get an zip archive.
Step 2: Login to your WordPress Dashboard.
Step 3: Go to Appearance > Themes. Click Add new button, located at the top of the screen or Add new theme.
Step 4: Click on Upload button at the top of the screen and browse for your downloaded zip file “Theme-Name.zip”.
Step 5: Wait while the theme is uploaded and installed. Once installed click on the “Activate Theme” link on the redirected page.
Step 7 : Congratulation you are now ready to use the theme. Check for theme documentation for next steps