If you are looking to install an IPA file on your device without a full jailbreak, follow these general steps using a computer: IPA Installer For IPhone: Simple Download Guide - Ftp

Understanding Cydia, IPA Files, and Safe iOS Customization

: An alternative to Cydia Impactor that allows for "Ad-Hoc" signing and easy drag-and-drop of IPA files from a computer.

: As of late 2019, Cydia Impactor mostly requires a paid Apple Developer account to work.

: Change themes, fonts, sounds, and animations beyond what Apple allows. Enhanced Functionality