A partir de los tres fotogramas, imagina una historia
sobre esta familia.
IOJO! Debes imaginar la historia
poniendo las fotos en un orden
diferente del orden del libro.

ah, so ustedes and nosotros are my 'go-to' if i am using spanish mainly in the states? interesting, but still slightly confusing, haha."

it seems that you are a little confused about subject pronouns. yo=i, tú/usted=you, nosotros=we, ustedes=you(plural), ellos/ellas=they.

in the case of vosotros, it is an informal replacement for "ustedes" in spain. similar to using "you all" in english.

even though it is not generally used in conversation outside of spain, it is used many times in literature. i would suggest having at least some familiarity to that form, at least to recognize what it is.