Log into your WordPress admin (i.e., your dashboard)
Go to Plugins->Add New
Go to Upload New
Find the plugin zip (from your downloads section)
Activate the plugin
After activation, you will be taken to the plugin's settings screen.
Download the plugin zip file from your account section.
Unzip the plugin zip in a place you can remember for the next steps
Log into your FTP program of choice for your website
Upload the unzipped folder into wp-content/plugins
Log into your admin dashboard
Head to the plugins screen
Search for Comment Edit Pro
Activate the plugin
After activation, you will be taken to the plugin's settings screen.