In order to upload the theme you have to :
1. Re-download the theme from themeforest: https://themeforest.net/downloads
2. Remove the actual theme that you have installed on your website (most likely, make a backup of this, if you do not use the child-theme)
3. Install the main theme, smartowl.zip file from the downloaded package, after this install the child theme, smartowl-child.zip located in same path as main theme:
This is an example for SmartOwl theme, but the folder structure for all themes are the same;
4. If you need updates for any plugins, deactivate them, and unninstall/delete. You will receive the “Begin install the required plugins” on the Plugins page from admin Dashboard.
Now you are set and good to go with your theme and plugins updated.