Generally, a guitar connection to iOS device looks like this:
Let’s see how it’s done in detail.
iPhone 7 owners: since there is no headphone jack in iPhone 7, get an adapter that uses lightning port for connection and has its own headphone jack.
Tonebridge supported devices: Alesis IO Dock, AmpKit Link, AmpKit Link HD, Apogee JAM, iRiffPort, iRig, iRig 2, iRig HD, iRig Pro, Line 6 Mobile In, Line 6 SonicPort.
Use a connection guide that came with your adapter. Each adapter has its own connection scheme, but the general rule is to plug the device into a headphone jack or a lightning port.
If your adapter has a volume control, be sure it's not set to zero.
Use any guitar cable with 1/4" jack. For example, like this one:
Plug one end of the cable into your guitar, and the other end into the adapter.
That's it! Your guitar should be connected now, and you can start playing.