Assuming you are talking about the new Call of Duty: Mobile battle royale mode, here is how you can use the wingsuit:
Once you have parachute jump into the map, look for a safe place to land. Once you have found a safe place, open up your inventory and equip the wingsuit. After the wingsuit is equipped, double tap the spacebar (or whatever button is bound to jumping) to deploy your wingsuit.
You will then fly through the air until you either hit something or release the button. While flying through the air you can change direction by moving your mouse or tilting your device left and right. You can also speed up or slow down by pressing W or S on keyboard (or up and down on mobile devices).