Introducing different language(s)?

[BabyGirl05]

I have a beautiful mixed baby boy! He will be a year old in 2 months. His dad is puerto rican and im asian. So the language we use in our house is english. However, when me and his dad are working and grandma is watching him, spanish is the main language at grandmas. It would be nice to be fluent in all three languages but figured learning my native language would be too hard unless it was the only language that was spoken. So i was wondering, how do i go about getting my son to become fluent in english and spanish. my boyfriends other kids understand some of it but do not speak it and we would like the baby to be able to speak it, if possible. I really think it would benefit him in the future being bilingual. So if anyone has ideas, please send them dis way! Thank u!!!!