Firstly calculate the measurement of each angle with a protractor. Then divide the measurement you have get by 2. Then draw a line according to the measurement you have get now. That's the bisector.
For example, if the whole angle measures 120°, then measure its half, i.e., 60°. Then draw a line. You may get an idea fron the pictures.
I cannot measure the angle of your picture so use the process that I have told you.
