SharePoint Tips: Customizing Your Views and Adding Columns
Customize your views and add columns when necessary
Sometimes, you might need to track a little more information about items in a library than SharePoint comes pre-configured out of the box to track.
For example, you might want to add a drop-down list that has choices about an item's status that users can select at various points during the lifecycle of that item. It's easy to add these choices to SharePoint list views so that you can work with these statuses.
In a document library, for example, select the Library tab from the Library Tools group, and then click Create Column.