My friend is similar. She's shy and quiet and somewhat reserved.
But placements are giving her the confidence and experience.
And she's enjoying the course.
I do recommend working as a hca either before you apply or if you get in, during the course. It helps massively and it builds up your confidence and skills as you go along.
What you do on placement will slightly differ from one area to the next. But in general you will be doing personal care, helping to change and clean down beds. You will be doing a person's clinical observations, doing documentation. You may get to observe operations. You may get chance to do injections, you will be administering medications and doing med rounds. It's all dictated by the area you're in, the field of nursing that youre doing and what the nurse does in that area.