How do you mud drywall joints?

apply the mud with a drywall trowel into the joints (you can get premixed mud) and press the tape into the mud. cover the tape with another layer of mud. let dry and sand it smooth. it may require more than one layer of mudding and sanding.

For inside corners use the same method, but fold the tape 90 degrees into the corner.

For outside corners nail up prefab metal or plastic corners and cover with mud, then sand.

hope this helps!