First, make sure you already installed the Elementor (Free or Pro) plugin.
Then install the CovidNineteen Elements for Elementor;
1) Download the plugin from your Codecanyon Downloads page ( https://codecanyon.net/downloads )
2) Find the plugin CovidNineteen Elements for Elementor and click “Download” button and click “Installable WordPress file only”
3) Then open WordPress backend Plugins > Add New and click to the “Upload Plugin” button at the top.
4) Choose the downloaded zip file and press upload & activate.
5) You can use all elements by using Elementor Edit Page > https://jmp.sh/qQGweYr