Cutting:
Seam allowances are included - 1cm wide or as per marking clips!
Cut the pattern pieces from your fabric. Position the selvedges parallel to the center so you can place the front and back pieces on the fold. The pattern pieces should all be placed with the lettering facing up. Always align the grain arrow on all pieces in the same direction and parallel to the selvedge of the fabric. Transfer all notches from the pattern by making a 3mm cut with scissors or chalk and mark the ends of the darts . Notch the seam allowance along the fold, as this is always the center. 
To sew this shirt you will need a sewing machine and an overlock sewing machine, or alternatively the zigzag stitch on your sewing machine to neaten the cut edges.
Be sure to use a jersey needle and a stretchy stitch. This means that if you're using a home sewing machine, you should use either a zigzag stitch or a three-part stretch stitch. Then, finish all seam allowances with a zigzag stitch or another similar stitch to prevent fraying. The colored lines in the images show you, in addition to the description, where a seam needs to be sewn or glued.
When sewing, pay attention to the seam allowance included in the pattern.
Have fun sewing!
First, stick a shaping tape over the neck hole (here: the blue lines). This will prevent it from stretching. You can find all the information about shaping tape and how to use it 
First, neaten the side, shoulder, neckline and hem edges of the front piece. 
Repeat the same step for the back piece. 
On the sleeve pieces, neaten the hem and the dividing seam. 
Then iron the hem of the sleeve pieces upwards. 
Place one front sleeve onto the matching back sleeve and sew the two together along the curved edge. Leave the hem folded up. Then press the seam allowance open. 
Next, you need to create the drawstrings. To do this, sew the seam allowance 1cm from the seam. 
Sew the underarm seam together and iron the seam allowance open. 
Finally, sew the hem allowance to the sleeve. Start behind the first drawstring and end in front of the other drawstring. Otherwise, you would sew the drawstrings closed. 
For the tunnels, you'll need four ribbons. You can make them as follows:
You can now pull the ribbons into the tunnels using a safety pin. 
Now you fix the open ends of the ribbons with a seam. 
Next, iron the hem and neckline on the front piece. 
Do the same on the back part. 
Sew the elastic band to the neckline at the center front, keeping it tight. The pattern has crosses to indicate the gather length. 
Place the front piece on the back piece and sew together along the side and shoulder seams. Press the seam allowance open again. 
Now stitch the seam allowances of the hem and the neckline. 
Finally, all you have to do is insert the sleeves and neaten the seam allowances together. 