How to update a plugin?
In order to update Cost Calculator to the latest version please download the plugin folder from the download section of your CodeCanyon profile.
Extract bt_cost_calculator file from the folder you downloaded, and upload it to /wp-content/plugins/ folder of your WordPress installation. You will be prompted to overwrite the existing files. Select 'Yes', and the plugin will update.
If you have made some changes in the plugin's code, you will need to reapply the changes in the new version.