What does "looking into the emitter" means in small signal analysis?
It means determining the impedance the emitter presents to an external signal.

Normally you'd do it by sending a small current, much smaller than any bias so as to keep the bias conditions essentially unchanged, into the emitter, and see what the change in voltage was. Impedance is then voltage/current.

It usually involves the Re, Ie, beta, and conditions around the base terminal.