To install the file "download-day-calc-calculator-pro-v8-univ-64bit-os120-ok14-user-hidden-bfi2-ipa," you will need to sideload it onto your iOS device. This process bypasses the App Store to install applications directly.
: Used to sign the application so it can run on your device.
Sideloadly is a popular, user-friendly tool for installing IPA files on iPhone or iPad.