Firstly clasp your hands and join your thumbs together.
Next open the clasp a little from between your thumbs so that a small hole is formed. Now with the upper part of your thumbs press a little more so that the opening is very small. Make sure that no air is escaping out of your hands.
Shape up the upper joints of your thumbs into a mountain and push the lower joints towards the inner side so that no openings are left. Make sure that the fleshy parts of your thumbs are tightly closed together.
Once your hands are shaped up rightly as described, its time to create the sound. For this separate your lips and bring your hands close to your mouth. Curl your lips and press them against the upper joints of your thumb. Make sure that your hands are in the right position as described in the previous step.
First take a deep breath and then immediately blow the air into the space that you have formed with your hands. Make sure that you blow the air while making a sound like too-wit-ooo. This will make a sound like an owl. Although the hands are tightly closed but there will be a small opening left that you cannot close anyway. This small opening is at the base of your hands that is found right below the palms and it is from here the air will escape.
Repeat the steps again in order to make the right sound.