So glad you asked! Check out these gifs.
1. Warm up your tortilla for 30 seconds in the oven! You'll probably have to fold it in half so it fits. No need to actually turn the oven on. Just use the residual heat leftover from cooking the burrito’s filling to get it warm. (This step is important because warm tortillas are always better AND because it helps the tortilla be more pliable. You'll be able to manipulate it without it falling apart.)
2. Spread the burrito's filling on the bottom third (or bottom half) of the tortilla. You want the filling toward the bottom so it's easier to wrap up neatly when you're ready to actually roll everything up.
3. How do you get a perfect burrito that doesn't leak filling? You fold the bottom of the tortilla tightly over the filling, then fold in the sides before you roll it up. (The bottom edge should be making contact with bare tortilla, then scooch that little pouch of filling wrapped in tortilla backwards a touch to "seal" it.)
4. Final step! Enjoy your burrito. Simple as that.