Once you have the files, you can then place them into the appropriate Ryujinx folder. For users who are not comfortable with this process, many reputable online resources offer the keys. However, it is strongly advised to only download from trusted sources and to be aware of the legal and ethical considerations.
If you are still encountering issues, here are the most common problems and their fixes: Ryujinx Prod Keys v18.0.0 - Latest Product keys...
Fix "Key Not Found" or "Firmware Missing" errors when launching newer titles. How to Set Up v18.0.0 Keys in Ryujinx Once you have the files, you can then