It doesn't replicate the shape it infests and takes over the original body that's already wearing clothes.
The new one is supposed to be a prequel, showing what happens in the Norwegian camp which is kinda dumb because we know they all die except two and then get shot by the Americans at the start of the next movie :/
Read The Things by Peter Watts if you liked the 80s movie, it's a retelling of the film from the point of view of the creature.
Available here