I share these steps since I didn't find them intuitive at first. That said, once I figured it out, I promised never to use the USGS Store again.
One warning: I understand that the quads downloaded from Google may or may not be the most recent versions. USGS and partners are working on fixing that situation.
1) Visit USGS Topographic Maps Gallery website.
2) Search for or zoom into area of interest. At right, Ottawa, KS.
3) Be sure "information" layer is checked "on." What is "information"? It's the red quad boundaries and the green point markers.
4) Select the green point marker and click the "Download From USGS" link. The GeoPDF file will be downloaded to your hard drive.