If you are interested in using hair extensions on your hair, you can read this article to know how to sew hair extensions. Or, if you want to learn it professionally, you can go for the Micro Sew-In Weave Hair Extension Course provided by the Rapunzel Hair Academy. With this course, you will know how to sew in hair extensions. 

We provide you with the steps for you to learn how to sew in hair extension:

1. Thread your needle: Trim a piece of extension about 48 inches long and insert it through the eye of a curved needle. Pull the thread through the needle and make both the end of the extension equal. Tie the loose ends together. 
2. Secure the weft firmly: A single hair extension is called the weft. For more volume, you can fold the weft in half. Then insert the folded end through the needle and secure the ends firmly.
3. Do the first stitch: With the weft attached with the needle and the thread, insert your needle through the cornrow and bring it up. A curved needle will make the work easier and the pointed end of the needle will be pointing towards you. 
4. Attach the extension: Now, insert the needle into the front of the extension below the seam, which is called the track. If you are using a folded weft, make sure the needle passes under both the tracks. Hold up the hair extension and try to cover the cornrow with it. Insert the needle back under the cornrow and pull the thread gently, forming a loop.
5. Make a knot: Once you bring the needle from behind the cornrow, insert the need at the end of your stitch and pull the thread through. You can continue sewing until the end of the row. 
6. Trim if needed: After sewing the hair extension, you can also trim the end as per your wish.

If you find it difficult to follow the above steps, you can just join a course and learn how to sew in hair extension.