By default, the dialog assumes you want to search in the source text, so the leftmost radio button at the top is on. You can type your search text in the visible text box. The search text does not have to be an entire word but can be any part of a word.
The default mode of search is case-sensitive meaning that that Adapt It treats "A" as a different character than "a". You can have Adapt It ignore the differences by checking the Ignore Case 
check box.
Adapt It assumes you want to search the lines without punctuation. If you wish to search the line with punctuation, check the Search in lines which retain punctuation 
check box. Adapt It then searches the line with punctuation. This feature is useful if you need to find a particular punctuation mark.
At times you may want to find a particular combination of words phrase, but you have not made them into a phrase. In this case, you need to have Adapt It, search for the words using multiple piles, not just one. To do this check the Allow the search to occur in text spanning multiple piles 
check box. This feature may be useful if you do want to convert the word combination into a phrase.
When you are ready, click Find Next to have Adapt It perform the search.