Ah I see.
Yeah, it's asking for the username / password of an account on the Pi (by default, pi / raspberry) , and the default SSH port is 22, unless you've changed it.
Please note that in more recent versions of Raspbian, the SSH is disabled by default, so you might want to check on the Pi itself if the SSH interface is enabled (step 2 in this documentation): https://www.raspberrypi.org/documentation/remote-access/ssh/
If it's still not behaving for you, you can do a manual install from the web dashboard by logging in, adding a new Pi, and following the on-screen instructions until you get to 'Option 2' where it gives you two commands to run on the Pi to install the Cayenne agent. Once the agent is installed and the Pi is connected to Cayenne, it will show up in the iOS app, even if you did not install it from there.