"I was reading that book yesterday."
Translation:wa'Hu' paqvetlh vIlaDtaH.
The suffix -taH indicates an ongoing action -- in this course, we translate it with -ing forms in English, e.g. "I was reading, I am reading, I will be reading".
This unit introduces vIlaDtaH more or less as a single vocabulary word to be learned; the suffix -taH is explicitly introduced in "Locations" and repeated in "Aspect", where that suffix will be used freely with other verbs.