1 month old has a cold

My daughter has a little chest cold, took her to the pedi and they did a chest X-ray and ruled anything out. She’s eating completely okay, no fever,a little bit irritable but the only problem is that I can actually hear mucus in her throat and chest, sometime she chokes for like a second on the mucus and she has a very mucusy cough.

What can I do to help the mucus since it’s not in her nose at all and she isn’t stuffy in the nose?????