I was approved for $827 a month but only used $679 I was told that I would receive the unused portion in my tax return this year. what do I have to do to get it?

how do I get the unused credit amount I was approved for with my health ins marketplace?

also, it says I'm suppose to fill out form 8962 if I received a 1095 a, which I did or did the system automatically fill it out for me since I'm filing online?