I will assume this is a Firefox for Android topic and transfer it from the Thunderbird forum.

I don't understand... I was trying to do this on a win10 desktop computer. Is this only for Android?

https://duckduckgo.com/app

well, I had never heard of this until you posted. But I googled the issue and found this web site. https://spreadprivacy.com/introducing-email-protection-beta/ Which offer these instruction which you cut out of that page I assume. # Download DuckDuckGo for iOS or Android # Open Settings > Beta Features > Email Protection # Click “Join the Private Waitlist." Right under that is a link to download from the relevant app store for Android or IOS/Apple Clicking on the Google store link takes you here https://play.google.com/store/apps/details?id=com.duckduckgo.mobile.android it displays the images, but you can't install it on windows 10 because it is Android software. Clicking on the Apple link https://apps.apple.com/app/duckduckgo-privacy-browser/id663592361 tells me "This app is available only on the App Store for iPhone and iPad." Searching the Microsoft store yields no results for duckduckgo https://www.microsoft.com/en-au/search/shop/Apps?q=duckduckgo So I guess you are plain out of luck because duckduckgo don't have a windows 10 app. There does however appear to be a privacy addon for Firefox that I am guessing is about the same thing as the app as it is a modified browser for privacy AFAIKS https://duckduckgo.com/app So sorry for my mistake in assuming it was in some way related to Mozilla software. I could transfer this to the Firefox browser forum as you appear to be posting using that product, but really your question fits in nowhere as it related to offerings from duckduckgo, not Mozilla.