Use the search fields at the top of the client page to search for and filter clients.
You can search / filter by the following:
Name
Family Size (e.g. typing 3 will filter by families of 3, typing any number greater than 10 will return 'Family of 10+')
Postcode
Phone Number
Note that for Name, Postcode and Phone Number the app will return all clients who have the search terms anywhere in the field.
You can clear all the search criteria / filters by pressing the Clear button.