Firstly you need to open the Task List form and then filter it to return a subset of records. This can be done in a variety of ways. The simplest is to right click on a bound control in the form, which will then give you a number of choices using the value in the control, or you can select 'Text Filters', 'Number Filters' etc, depending on the data type of the column to which the control is bound, for further simple filter options.
To create more complex filters you can use the various options in the 'Sort & Filter' area of the 'Home' ribbon.
Once you have filtered the form you can click on the Save Filter button. This will open the Filter Details dialogue form in which you can name and describe the current filter, and close the dialogue form to save the filter for future reuse.
Having saved one or more filters, you can filter the Task List form by clicking on the filter button between the Search text box, and Save Filter buttons in the form header. This drops down a list of your saved filters, along with a couple of other options. By clicking on the name of a saved filter in the list the form will be filtered to the records determined by the saved filter.
You can turn off the current filter by clicking on the 'Filtered' option in the navigation bar at the bottom of the form. Its caption will change to 'Unfiltered'. Clicking on it again will apply whatever filter was last applied to the form.
I don't have the Event Management template installed, but I imagine that the process will be similar in that.