In order to locate the Item(s) in which you are interested the list can be filtered on a number of criteria, including a text search. Navigate to the list of Items for a Project and click on the Funnel icon in the Header bar.  This will display the filters that are available. 

To use a Filter on Type, Status, Priority, Assigned To, Owner, or Tags click on the downward pointing arrow next to the Filter's name to display the values available for selection. 

This will display only those Items to which the selected Filter(s) apply.  In this case Item Types Activity and Task. 

To search type the text you wish to locate and the search function will scan the Item Number, Title and Description once you stop typing.  To locate an Item based on the Date From or Date To enter dates in the relevant boxes. 

To clear all Filters click on the Funnel icon with the line through it and to close the Filters click on the cross.