Bro you can't install directly. Magisk must be installed on your device and you must have root access rights. Then you have to use root explorer.
- Copy downloaded mod camera file to /system/priv-app/MiuiCamera/MiuiCamera.apk.
- You should set permissions 0644.
- Clear cache&data camera apk...
Exactly what do you want to do? You want to flash stock raphaelin firmware? if so, you can download raphaelin fatsboot rom, extract it, you can edit marked with two lines in flash_all.bat.
Everyone's so many different requests, but I can share a link to modded camera files.
*Don't forget to set permissions after copying the new camera file.
*Settings/Apps/Manage Apps/Camera -> Clear data -> Clear all data
https://yadi.sk/d/X73NP4YvWKW3GA