1The file
An IPA is the package an iOS app comes in. Bring one you own or one you trust: Sideloadly installs any IPA you hand it.

Sideloading iOS apps typically requires a jailbreak. Sideloadly installs any IPA from your Windows PC or Mac with a free Apple ID.
The download page asks whether you use Windows or Mac.
Each step below matches a number on the picture above, so you can see where you are.
An IPA is the package an iOS app comes in. Bring one you own or one you trust: Sideloadly installs any IPA you hand it.
Plug your iPhone or iPad into your Windows PC or Mac, drop the IPA into Sideloadly and sign in with your Apple ID. A free Apple ID is enough, no paid developer account.
Drag the file onto the phone.
The app appears alongside your others. Before its first launch, iOS asks you to trust your Apple ID in Settings, under General, then VPN and Device Management.
With a free Apple ID the app remains valid for 7 days, and Sideloadly's auto-refresh signs it again for you.
I have to jailbreak my iPhone first.
Sideloadly signs the app with your Apple ID. Your iPhone stays exactly as it is.
Only a paid developer account works.
A free Apple ID installs apps. A paid account only keeps them valid for longer.
Once it's installed, it stays for good.
With a free Apple ID an app lasts 7 days, and auto-refresh signs it again so you keep using it.