First switch on the transmitter and then the battery in the drone. Attention: the quadcopter must be in contact with the ground when connecting (height sensor must know proximity to the ground, calibrate). By the way, you can only start the quadcopter by pressing the takeoff button. I hope I could help you further.

Hello Apollyon
Push the left lever all the way down, don't let go, and turn on the remote.
Connect the battery to the copter, this should connect. If only the tail light is still flashing, that doesn't mean anything, the other lights will be steady.
Take-off is only possible with the take-off button, then you can steer. Do not move the left lever all the way down.
Hope this helps!