Welcome to the iNatForum!
The Explore tab lets you draw boundaries, either rectangular or circular, around an area. If you’re not sure where on a map a particular set of coordinates are, you can use the following two links (for a portion of Central Park, in New York City) and replace the coordinates with the ones you want.
Coordinates are in decimal degrees. For the circular boundary, the radius is measured in kilometers. For the rectangular boundary, you’re specifying the northeast and southwest corners of the rectangle.