I never learned how to sew properly but I’ve taught myself how to do a couple simple things and they’ve worked out well so far.
For a button you just thread the needle and tie a big knot at the end of the string (so the thread doesn’t slide through the coat fabric). Push the needle through the coat fabric (starting in back so the knot is hidden) where you want the button and slide the button on the front. Then just see the button on using plenty of thread to make sure it’s secure. Lastly come up from behind the button with the needle and make several tight loops between the button and the fabric, basically just binding the thread behind the button so the button sticks out from the fabric a little. That’ll make it easier to button up because it won’t be pressed against against the fabric.