Hello and welcome to the forum,
There is a LOT of info in the Enterprise COBOL Language Reference that is available free online. It has several examples. You probably want to download a copy for easier reference. Also, suggest you download a copy of the Enterprise COBOL Programming Guide. You should (will) use both regularly. We old guys still do. . .
Suggest for learning you restrict yourself to a one-dimensional array for the first attempt. Define a "code" and a "description" and using the code, find the description. If you get stuck, post your code and someone will be able to help.