How to e-file schedule 8812 with 2021 income tax return to claim the remaining credit

We're eligible to get $3000 credit for my kid, but we only got $1500 from Oct. to Dec. 2021.

I did not find a place to claim the remaining credit when I e-file the tax return. The SW just asked me to input the Box 1 on letter 6419 ($1500 only).

How can I claim the remaining credit thru e-file?

If I can't, can I e-file without it, and file an amended tax return?

Thanks.