Water them, increase shade, increase humidity, reduce temperatures.

One of those will fix it (or all of them).

At this time of year, they are selling them as temporary indoor flowering plants. Various retail establishments do this as it gets close to Valentine's Day.

I need to stress the 'temporary' part of my comment. Hydrangeas are not intended to be houseplants and they don't make very good ones. Indoor conditions are typically too warm for them, too dry and with inadequate light. To increase this plant's longevity indoors, keep it in a very cool location with bright but indirect light and keep the soil evenly moist but not wet.

Depending on your location and IF you can keep it alive long enough, it is possible to transition these plants to the outdoors at a proper planting time. Possible but not very probable.

What were the outside temps when you brought them home?

tj