Severe weather spotter training, aka "spotter talks", are usually hosted by various amateur radio or public service groups around the area. These sessions are usually conducted by personnel from the National Weather Service office in Indianapolis.
For a list of scheduled spotter talks, click here. Most spotter talks are scheduled in the late winter or early spring to prepare for the upcoming severe weather season.
You will also find at the link above downloadable spotter guides and an online spotter training video.