Please tell me what to do, in details if possible, my 3 months old has a cold?

First of all give clear liquids, juices and H20 as much as possible, okay the nose bulb you put in nose and squeeze it and it should remove some of the mucus and ............also try to give a wash up and not a full bath for about 3-5 days. after that do vaporizer. If you like run shower to make bathroom steamy and then take baby in there and that should also relieve some stuffy nose. I hope baby feels better