At the top right of the window throughout the app you will see a search icon (magnifying glass). Clicking on this will take you to the search window. Enter a search string and then hit the search icon at the bottom right of the on-screen keyboard. A scrollable list of search results will be returned, sorted by relevance. If you wish to change your search just click on the search input again.
When interacting with our website you have the option of creating saved searches. For more information you may read this article titled "How do I create a saved search?" You may access these searches from within the app by opening the app's navigation drawer. The Saved Searches list can be found in the "Workspace" section. Clicking on one of the saved searches will execute the search with the same parameters you saved, including sort order.