^^^ what he said
I recommend going to the Analysis feature (https://www.chess.com/analysis), setting up the position you want to play, then hit the "Practice vs Computer" option.
Most of the bots have preferable openings when you read their description, as example this person likes the Dutch. A positional bot will open up with d4 or c4 as another example.
What I was doing when I was learning to defend against d4, was found a character that exclusively played d4 or if they had a couple openings in their reportorial, I would hit the “take back” button and they’ll switch the opening.
The trouble is, when I play black, I don’t remember as well what to do, because the computer always plays something different. I need to get to know black’s defenses better. It would help to see one consistently and learn it, and then move on.
Is there any way to make the computer always defend with the Sicilian, for instance?