how to get rid of damp in your room?

got damp at bottom of one of my walls in living room, paper peeling off and getting white dots underneigh paper that coming on, when you put your hand on it feels damp and soggy also smelly, i also have a tiny bit near my back door which has been there since i moved in thats not paper just paint on plaster

what can get rid of it? im in private rented house

thank you