I think you need to more build up your imagination not that it’s weak. If you haven’t read all that much you are not used to doing that. Try to read stuff that is A.Interests you, B. Is not to wordy (although it helps with small details, with a weakened imagination it just becomes confusing) and C. Short. If it’s too long your mind will definitely wander. Also reading stuff you are familiar with will be easy and train your brain to imagine like a modern story with cars and tv’s. Don’t rush it’s fine to start slow and even re-read more times than you’d care to admit. It may take a while, but try to enjoy the journey and you’ll reach the destination without even realizing it.