You absolutely need a fan: when riding on a home trainer, you sweat much more than outdoors because there is no airflow. Without ventilation, heat builds up quickly, the session becomes uncomfortable, and your heart rate rises unnecessarily. A simple floor fan or one placed on a piece of furniture, directed toward you, is more than enough. What matters is having a steady stream of air to keep you cool.
Also plan on dedicated clothing: a light jersey, comfortable bib shorts, and a towel within easy reach. And always keep something to drink nearby. On a home trainer, you lose a lot of water, even during an easy session.
Fan example
Bib short example