There are a few ways, but the simplest is probably:
Select it - and be sure that it is the 'right' one to delete, click 'Edit Layout' from the toolbar or View>Layout Mode from menu bar, then Layout>Delete Layout.
Note that this has no effect whatever on the fields or data in your database, it's only deleting a display of those fields.
Thank you. I was able to delete the fields so that the layout is empty, but is there a way to delete one of the layouts from the document list? When I go into "documents" it still shows two "customers".
As Symbister has already posted, Layout | Delete Layout will delete the entire layout. "when I go into documents..." since we don't know what starter solution you are working with, we don't know what you meant by "documents".
Typically, a table in FileMaker has a table occurrence and a layout of the same name. Deleting the layout does not delete the table occurrence nor the table of the same name as they must be deleted elsewhere. Thus it's possible to delete the layout, but find the same duplicate table occurrence names in a drop down list of table occurrences--and there are mnay such drop downs in filemaker, but none would appear to be what you are referring to when you refer to "documents".
Likewise, deleting fields from the layout do not delete them from the database, it only means that those fields are no longer visible on the layout where you deleted them.