@KAT75, you need to be more specific. What app? In general you use Search on the Home Screen left-side menu or Search within "Streaming Store" to find an app to install. You can also use the website: https://channelstore.roku.com. Note that for reasons only Roku could explain, Search isn't available in all regions/countries.
Roku Community Streaming Expert
Help others find this answer and click "Accept as Solution."
If you appreciate my answer, maybe give me a Kudo.
I am not a Roku employee.