Once you understand the assignment, you need to choose and then probably limit (or focus) the topic. The following has information you can use to do just that.
Points to Consider
Choose something which appeals to you.
Your topic should be neither too broad nor too narrow.
Your topic should lend itself to the type of speech or project you are creating.
Places to Go for Topic Ideas
Look around the room; see if something inspires you.
Talk with friends or family.
See what's trending on Twitter.
Search Google -- you may find an organization's website that will help you broaden or narrow your topic.
Check out Wikipedia articles -- don't use the article as a source for your project, but the article may help you by identifying people, events and organizations -- the table of contents is also great when your topic is too broad.
Watch the news, or read a newspaper or current magazine.