STEM / STEAM is very broad. Based on your interests, ability and your students' abilities / interests, you can do -
* various engineering topics like mechanical, civil, aerospace, electrical, electronics, environmental, sustainability, bio-medical, or
* learning computer programming or coding. With many different languages available you have options here like Java, HTML, Python, etc. Or, for a beginner, you can pick one of the drag-and-drop type programming like code.org or Alice.
* a technology centric program like robotics using Lego, Vex, Sphero, etc.
* a business, communication, marketing, citizenship, social, equity or finance related theme that can take any of the above and give it a little different twist!
* an applied innovation wherein you take some of the fundamentals from the above and coach students to create and innovate. Today, communities and parents love creations involving Artificial Intelligence (AI), Machine Learning (ML), Internet-of-Things (IoT), robots, etc.