My 11 month old has yellow mucus comimg out of her nose plus she sounds congested. What can I give her or do?

Cold. If this has been only a few days that this is happening then give your little one plenty of clear liquids. Use a humidifier, saline drops in her nose and bulb suction. If the symptoms have been present for more than 7 days make an appointment with your pediatrician.
Bulb suction. Even though babies hate it, using bulb suctioning is an excellent way to remove mucus from their noses. Humidity is also important, especially in the winter. If the yellow discharge doesn't improve, see your physician - sometimes a cold can become a bacterial infection, which requires antibiotics.