We are Reiki, so that is happening whether we are awake or asleep. What you can do is set your intention before sleep: place your hands on your body, bring your awareness to being Reiki, and let that be the last thought of the day. Your hands will fall away once you sleep, and that is fine.

I cannot know without seeing you practise, but the question itself says you are not confident, and confidence is the whole point of the symbols. They were added to the system of Reiki to give people something tangible to draw, say and chant so they could feel the energy. They are there to support you, not to be worried about. Practise what you were taught and let it take you in.