I am a new immigrant (PR). I want to apply to UCCB and CCTB. I just have SIN number & bank account with me. How can I avail the benefits?

I am a new immigrant (PR). I want to apply to UCCB and CCTB.

I just have SIN number & bank account with me.
I landed 2 months back.
I have not files any return in Canada till now.
I am trying to create CRA account with SIN number but doesn't work since website gives error.

How do I avail benefits?
And when can I start getting it?
How much would I get for CCTB and UCCB?

Thanks