Once you're in Warrior I and spend a few breaths there, you can transition into Warrior II, the next step in a Sun Salutation sequence. In Warrior I, your hips and torso are facing forward; here, you will shift the stance of your feet and open your hips, turning to face the side of the room.
From Warrior I, with your front knee bent and your heels grounded, spin your back toes out so that they're at 90 degrees, pointing at the side wall. Lower your arms so that they're parallel with the floor, straight out on either side of you, as you slide your hips open to the side. Your body should now be in one long line with fingers pointing to the front and back of the room. Keep your front knee bent over the front leg, and keep your back leg straight. Repeat this pose on both sides.