Start by washing your hair as usual, using the shampoo you normally use. Do not massage the shampoo in, since it can create more tangles in your already tangled hair extensions.
Apply a leave in conditioner liberally to your hair and extensions. Let it sit in your hair for five minutes. Then, with the conditioner still in, gently comb through your extensions and hair with your fingers, to detangle as many knots as you can.
Rinse your hair thoroughly with water. Once the conditioner has been rinsed out, do not towel dry your hair. This may cause more tangles.
Take an untangling hairspray and spray it generously all over your hair. You can easily find an untangling hairspray in the baby care aisle of any drug store. The best thing about these sprays is that they do not make your hair oily.
Then, take a wide-toothed comb and start combing through your hair. The wide-toothed comb will do less damage to tangled hair than an ordinary brush. Start from the tips of your hair and move up to the top of the head after having combed through the tangles at the very ends.
If the synthetic hair extensions are severely matted and tangled, try loosening the knots using the tips of your fingers.
Once the hair and extensions are combed through and you have taken all the tangles out, blow dry your hair. Blow dry the hair in sections while continuously brushing your hair with a paddle brush.