Errr...
What selection step???
Here is the Buffer tool :
![BufferTool.jpg](/legacyfs/online/140277_BufferTool.jpg)
Input Features : presumably your points
Output Feature Class : what you want to call the output, usually something like MyInputName_Buffer.
Distance : either a fixed number, or if you click the filed radio button, a field containing a number for the distance. If you had another column with a distance (calculated from your "severity" perhaps), that would go here.
End Type & Method... Usually leave alone.
Dissolve : None - individual buffer polygons will be created for each input point.