Question

Change the verb to indicate that it was in progress at a time in the past using the correct form of Estar in Blank 1 and correct form of action verb in Blank 2.
Nosotros subíamos a la habitación.

Answer 1

Blank 1: estábamos
Blank 2: subiendo 

(Nosotros estábamos subiendo a la habitación)

Answer 2

I don't really understood your question, but i guess that you want to change the sentence to past progressive, in that case it will be like this:

Nosotros estábamos subiendo a la habitación.