To generate the certificate necessary to send push notifications through an iOS app, first log in to the Apple Developer page and navigate to Certificates, Identifiers & Profiles. Then, create a Certificate Signing Request by clicking on the + button, selecting "Apple Push Notification service SSL (Production)" and continuing with the process. After generating the CSR file, upload it, click Generate, and follow through with the registration process. Finally, download the certificate, install it into Keychain Access, export the private key, and save it as a .p12 file. Once you have the .PEM file, you can send push notifications to your app users using Instabug.