Best way to replace data

I have numerical data (accounting system numbers) that I want to replace with alpha characters (accounting system account number descriptions). I have created a worksheet that contains the numbers in Column A and the Descriptions in Column B. I think that using VLookup might work for this but I have not used this before. I remember learning it sometime back but am fuzzy on the process. Is this the best way to accomplish what I want to do? Can I have the lookup table in one worksheet and use it in another. I seem to remember this as a problem???? Any help or ideas of a better way is appreciated.