Doing a search with GoBase means entering a position on the Go board and next specifying which part of this position you would like to search with GoBase. You can select the snapshot you're interested in by dragging a rectangle with the left mouse button while keeping the <CTRL> key pressed. A red rectangle will indicate the selected region:
The moment you release the left mouse button the region will be fixed. This is indicated by a change of color of the selected snapshot. At this very moment also the Search button will be enabled:
Note Some hints for selecting regions are included in section Tips.