This is the 17760th most frequent Russian word.
укрыться
"To shelter oneself" or "to cover oneself."
In this sentence, 'укрылись' is used in the context of sheltering oneself with an object for warmth.
Мы укрылись пледом, чтобы согреться.
We covered ourselves with a blanket to warm up.
Here, 'укрылись' indicates hiding or taking cover to protect oneself from natural elements like rain.
Туристы укрылись от дождя под зонтом.
The tourists took cover from the rain under an umbrella.
In this context, 'укрылась' conveys an action of seeking protection or hiding to avoid heat.