How can I photograph a tent glowing at night?

Use a tripod and treat it as a night scene with controlled light inside the tent. A long exposure is typically used to capture the dark surroundings and sky, while the tent is illuminated separately from inside.

Two practical approaches:

• Continuous light inside the tent: use a diffuse light and experiment with brightness versus shutter time. The longer the exposure, the dimmer the light should be to avoid blowing out the tent.
• Flash inside the tent: expose for the night background with a long shutter, then fire a single flash inside the tent to make it glow. This is often easier than balancing a continuous light source.

Tent color matters less than the color of the light; changing the light color is usually easier than relying on a specific tent fabric. A lighter, translucent tent will generally show the glow more clearly.

So the basic setup is: camera on tripod, compose the night exposure, place a diffused light or flash inside the tent, and test a few combinations of shutter speed and light output until the tent looks bright but still retains detail.