My age is 21 & weight is 46kg.
I desepertely want 2 increase my height.
So what should I do.

The only legal way to increase your height at this point is to grow some more naturally. You could try eating a lot more, but at this point, it really is not going to help.

If you are a male and below 5 feet tall, you can ask your doctor about growth hormone.

An inversion table can increase your height if your spine is compressed. When we began to use them, most of the people in my family grew about an inch and a half or so just from decompressing your spine. Also, getting a deep tissue massage can help decompress your spine.

There is no way to make yourself taller, we are the way God has made us and all we can do is learn to be happy with who we are.