Hola Andy
There are two questions related to this lesson which are using the verb "irse" in the imperative. These two sentences are:
¡Vayámonos de aquí!
(Let's get out of here!
This is conjugating irse in the nosotros form of the imperative (for nosotros it is the present subjunctive form), and has the pronoun nos attached.
¡Vayánse de aquí!
(Let's get out of here!
This is conjugating irse in the ustedes form of the imperative (for ustedes it is the present subjunctive form), and has the pronoun se attached.
I hope this helps,
Saludos
Inma