The Create File List task will create a

File List Variable

based on the filters specified in the File Set. This variable will contain the file paths of the files found. That variable can then be used in other tasks by specifying that name in the

Input Files Variable

attribute. The 

Number of Files Found Variable

will contain a count of the files, which is useful in other tasks by using the

Execute Only If

condition and checking to see if the number of files found is greater than zero.