Hi Neepunjika,
Body language is the reflection of your confidence. You cannot generate good body language.
Your personality is the reflection of your character, thoughts, habits, attitude and knowledge.
If you build up these aspects then automatically these will reflect in your personality and body language.
To start off, you can do these immediate things to improve body language::
1. Smile more
2. Sit / stand straight.
3. Be ready to help people.
4. Be positive about the future and the environment
5. Pick up good habits from others and try to follow them.
6. Read more books
I think this will give you a good start.
Riyaz