You will notice on this page that every entry contains a TAG at the end, which is the name of the group. You will also see two drop down arrows in the search facility.
Click on the down arrow next to NAME and then click on TAG
Click on the down arrow next to IS and then click on CONTAINS : now trying adding the name of the group you are interested in.
You can try experimenting with other items under the drop down menus, but the above suggestions are the quickest and most reliable.
Click on individual events for more details