My 23 month old son, does not sit still so mom and dad can teach him words.?

he knows a few words but does not put them together yet, I (dad) sit and try to teach him words by flash bards,books or other things we bought but doest not sit still, everything is play for him. We tell him sit down and listen but does not pay attention. most of the books he likes to rip the pages out, or just throw them around. how can i get my son to pay attention so we can teach him properly in a calm manner? is this normal behavior with other children? I know he is barely 23months but he should be saying more words and putting them together by now. he goes a lot of jibberish talk and points to things, he does know maybe 15-25 words but thats about it. what do you think? just fyi.. we are bilingual and mom and dad is not home all day we work and grandma takes care of him, grandma doesnt really teach him during the day either.