Click on the link above (https://client-portal.io/thanks-sumoling/)
Choose the Multi Site (2 codes required)
For Single Site, enter your discount code and click apply. You should see the total drop down to $0.
For Multi Site, enter both your codes one after the other and the same will happen.
You should receive a purchase receipt which will have the plugin files, a walkthrough video, and your license key. (This is also on the confirmation page).
Here's how to activate your license:

Upload the plugin to WordPress (Plugins -> Add New -> Upload)
Activate the Client Portal plugin
In the left hand sidebar, navigate to Projects -> Client Portal License
Paste your license key in the box (you'll find your license key in your purchase receipt email).
Enjoy!

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