Tips for defensive tackle and offensive tackle?

im a freshman at my highschool. im 6'4-6'5 and weigh about 260 pounds and im on the freshman football team and it is my first year playing. The coaches have me playing offensive tackle and defensive tackle. For the first couple of practices i really had no idea what i was doing and i was really out of shape. When we started our first contact practices i did really well. We were practicing pulling and i flattened a bunch of kids and when we were using the sleds for defensive line drills i sent the sled dummy up in the air. The coaches took note of this and said in our scrimmage i would get reps with the 1st string offensive and defensive line. In our scrimmage i did pretty good but i injured my knee and i just started practice last week. Due to my absence i pretty much lost my positions and i need to earn it back. What are some tips for being successful at offensive tackle and defensive tackle?? i noticed i sometimes have trouble blocking the smaller and more quick defensive linemen.