Hi Desirea,
ModuleSettings are meant for storing feature instance level settings for CMS plugin features. I would not recommend trying to access them from user sign in event handler. There is no context of a cms page or page contained feature instances at the point when a user signs in. I would not recommend doing this.
ModuleSettings can be obtained if you know the moduleid
using mojoPortal.Buxiness;
using System.Collections;
HashTable moduleSettings = ModuleSettings.GetModuleSettings(moduleId);
then you can get individual settings by key from the hashtable but must make sure they exist first.
Hope it helps,
Joe