Communication with the subconscious is fully possible. It just depends on your lucid state and whether or not your subconscious will come talk to you. Then again, there are a variety of ways to communicate with it as well. The first step that I would do would be to name your subconscious something unique like "Blue 42" or "Narley99". Tell yourself in your mind "Subconscious, your new name is..." a few times a day and it will inevitably recognize this.

The best way to get direct communication would be through a lucid dream, but that doesn't mean you can not communicate with it when you're awake. When people program things into their consciousness, or if they're meditating, this is a perfect point to where you can atleast send messages to it, ask questions and await for an answer. This is how changes in the physical body or mental state can change. If you want to gain 20 pounds of muscle, sit down and meditate about 10-20 minutes a day asking or telling your subconscious to grow 20 pounds of more muscle on your body. OR if you wanted to increase psychic awareness, this would be something to practice as well. There's countless possibilities with it.