If your question is not covered here, you can also try the Frequently Asked Questions page.
Help for newbies will be added soon! Really, it will!
The Model Info Pane gives information on the current Make and Model selected using the boxes to the left.
Each of the classifieds sites searched by HanksHelper has its own list of models. Some less common cars may be listed at some of the sites, but not others.
ie: The Ford F450 is listed at Cars.Com, CarsDirect and Oodle, but not AutoTrader or Automotive.Com. The F150 is of course listed at all five sites.
The model info tab shows which sites support the model you have selected. When you run a search on all sites only these supported sites will be opened.
Each of the classifieds sites searched by HanksHelper has its own list of models. Some less common cars may be listed at some of the sites, but not others.
ie: The Ford F450 is listed at Cars.Com, CarsDirect and Oodle, but not AutoTrader or Automotive.Com. The F150 is of course listed at all five sites.Therefore, if you have chosen to search only one site, using the "Sites to Search" button at the bottom-left, only the models that can be found at that site will be listed. To show models available at all sites, change the "Sites to Search" box to "All Sites".
The optional keywords box will allow you to filter the results for certain.. well.. keywords. By default, the sites all interpret keywords as "AND" searches. In other words, you will only see results that contain all of the keywords you enter. I hope to expand this eventually, but for now, AND's what we've got. 
HanksHelper currently allows you to automatically search the five best auto classifieds sites in the U.S.:
AutoTrader.Com, Cars.Com, Automotive.Com, CarsDirect.Com, and Oodle.Com.Normally you will want to leave the "Sites to Search" box set to all. However, if you wish to search only one site, or search for different models at different sites, you can use this box to manually select them.
) button and it should be fine.More tips will be added as they come up! Also, please check the Frequently Asked Questions.
Enjoy!