You can search within your script (or any document in the binder) for a particular keyword, phrase, or character. Any mention of what you search for will be highlighted in the document and you can then jump to those moments directly.

With your document open, click the magnifying glass in the upper right corner, next to the various annotation tools, to open the search tool.

Similar to the web app, the search tool can be accessed by tapping the magnifying glass in the upper right corner of the document you're viewing.