"How Can My Husband Adopt My Son Legally?"

Good Morning people. Please experts in the house I need an urgent reply.

I got married recently but had a son already. My husband wants to adopt my son legally so that he can file his papers for easier and faster migration into the US. My son will be 10 this August.

Searched everywhere on google on the adoption process but didn’t find suitable information. Please how do I go about this??