Finding a place to work on some fundamentals is great! When I first started a few years back, I watched a number of youtube videos on basic trail tips and went and practiced it all a little on each ride or just outside my house if I was bored. Learning to weight/unweight the front and rear and pick either up at will really helped transform my riding. Ride a lot and work on extending ride lengths to get the fitness up.
If you can, find a group of experienced riders that is happy to ride with newer folks. You will pick up a ton from riding with more experienced people, both on bike technical skills and off bike maintenance and "mtb etiquette."