Find a place in your house with adequate lighting and make sure that lighting is in front of you and lighting your face versus behind you or to the side creating shadows
Set the camera on your computer or device slightly above the level of your face so that it is angled down on you versus looking up your nose
Use the filter on Zoom if it helps you feel more confident on calls. This is just a button you can click so that it smooths our your appearance while on calls, kind of like a snapchat filter