To show the screen on a laptop connected by HDMI,
- Go to OBS
- Select "Plain - Primary Slides" from the list of scenes in the lower left corner
- Right click -> Full Screen -> Display 2 (It might be a different display number. If you choose the wrong one, click ESC and try again.)
- That opens a new window that should show on the projectors, but you might need to move the window to a different monitor.
To show a browser window from the streaming computer,
- Close the second OBS window that's showing the slides.
- Move the browser window to the monitor corresponding to the projectors.