hello,
Apologies for the delayed response, mapmyth.
The Timeline plugin lets you create a timeline as an Omeka Item with a type of 'Timeline'.
1) Create an Item in Omeka, and choose 'Timeline' for the Item Type. Then, choose a tag from the drop down in the Item Type metadata form. This tells the timeline to get all the other items in your archive with this given tag, to display those on the timeline.
2) Save then item, then you can go to the timeline item's view at example.com/timelines/show/2, where '2' is your specific item's ID.
You can also use a custom query of items, but you'd need to do the query for these, and add the display for it, directly to your theme.
We're in the process of updating the Timeline plugin to make it possible to, among other things, choose your custom list of items for the timeline from the Omeka admin panel instead of programmatically. We're hoping to release these update before the end of the year.