How to Add a Column to a Library
1. Open the Library that you want to add a Column to.
2. On the Library Tools tab, click Library to open the gallery of commands specific to the Library.
3. On the ribbon, click the Create Column button.
4. In the Name and Type section, enter the name you want to have in the Column name box.
5. Under The type of information in this column is, select the information type that is going to be described in the column you are creating.
6. In the Additional Column Settings section, type a description in the Description box (this is optional).
7. To allow the new column to be automatically viewed when anyone first opens a list or library, select Add to default view.
8. Click Ok.