Well, lookie what I found after clicking on Help.
Q: How do I define a specific area for download by entering coordinate values?
Enter a coordinate value into the Search window, such as 32.5 -98.25 in decimal degrees.
Zoom to the coordinate value.
Select Draw Annotation from the 'More' menu in the Search Results.
Enter a new layer name (such as Extent) for the first point.
Define annotation name of the first point, such as Pt1.
Change fill color to a more recognizable color other than white if you want.
Click on Draw.
Repeat Steps 1-3 and 6-7 to enter additional coordinate values, but also follow Steps 9-10 for each new point instead of Steps 4-5.
Specify the same existing layer (Extent) for each new point.
Define unique names, such as Pt2, Pt3, and Pt4, for annotation name of each point.
Review point locations under User Added Content.
Use the 'Zoom In' tool from the Standard toolbar to drag a box that includes all drawn points.
Select the 'Download Data' tool.
Click to download by current map extent.
Select themes and formats for download.
Choose appropriate products under each theme.
Select 'Checkout' after review of selected items in Cart.
Enter e-mail address twice to place order.