My topic sentence is:
There are many symbols in The Lord of the Flies that indicate the inability to remain civilized.
Typically you can provide a smooth transition from the topic sentence to the supporting detail sentence by using a transition word or transition phrase that indicates specific evidence.
You could use the following: Specifically, For example, In particular, etc. The following link, http://www.teachervision.fen.com/writing-composition/vocabulary/1780.html, has a great list of introductory words and phrases.
Your topic sentence is typically the claim you're making so you want to give an example of evidence before you develop the analysis for that particular body paragraph.