First of all you need - download repository.
Second - open and evaluate Installer.nb notebook.
Third -you can create your own new notebook for working and evaluate
Get["CustomImportExport`"]
For import file evaluate next
dataIn = CustomImport["YourFileName.sgy", "SEGY"]
You can see and analyze headers of traces
dataIn["TraceHeaders", 1;;-1, {"gx", "gy"}]
in this string we can see coordinates of geophones. In this package SeismicUnix notation of headers is used.
In next string you can get the values of first trace
dataIn["Traces", 1]
You can plot data (Seismic section or Gathers) by the way Christopher showed.
If you have questions - please write!