How do I group within a variable?

We have been trying to make groups within a variable for a large data set we have. I attached a picture of the data we're working with. It's part of a huge table we have called CVC_New. We are trying to categorize the different variables like so; underweight(1) = 10-18.4, normal weight(2) = 18.5-25, and overweight(3) = 25.1-29. If you have any advice it would be greatly appreciated!!

Hi!

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