1. Before Update
Download The Theme From ThemeForest
Log in to your ThemeForest account and download the latest version of the theme from there. Choose the Installable WordPress file only option.
Move Your Code to a Child Theme
If you made any changes to the theme files, move your code to a child theme. This is very important, as with the update all theme files will be overwritten and as a result, all your changes will be lost.
If you are an advanced user, making changes to the code, please always use a child theme! It will save you a lot of trouble and keep your customizations intact.
A basic child theme is already included with Dentalia and you can get it from ThemeForest. Download the full theme package (All files & documentation) and unzip it. The dentalia-child-theme.zip file is located in the child theme(developers) folder.