You cannot just tap an IPA file on your iPhone and install it. Apple blocks that by default (sideloading restrictions). To use an IPA library on iOS 9.3.5, you have two primary methods.
On Sunday, Joan called. Her voice was quick as a knit pattern—efficient and kind. They exchanged stories about Mae and the recipes. Joan told him how Mae had once delivered a box of kitchen towels to a nursing home, insisted everyone share lemon drizzle in the common room, and how she had kept her notes in that tiny app because "it's like a proper book and it doesn't flutter away." They laughed about the smallness of some things that nevertheless anchor us. ipa library ios 9.3.5