Step 1:
This is just an example of which papers you can use for the flowers.
Prefold in half four times.

Step 6:
Fold the flap upwards.
Repeat steps 3 to 6 on the backside.

Step 5:
Press the edges downwards / flat, see arrows.

Step 2:
Fold over the two lines at the bottom right, then over the two diagonal lines. And then over the two lines at the top left.

Step 4:
Fold the tip downwards.

Step 3:
Prefold over these two lines.

Step 10:
Fold over these four lines

Step 8:
Fold the flap sidewards. Do the same with the other three flaps.

Step 9:
Open the petal, see arrows.
Do the same with the other three petals.
 

Step 7:
Fold the flap downwards over this line. Do the same with the other three flaps.

Step 16:
The backside of the flowers are attached with safety pins.

Step 15:
I used safety pins to attach the flowers to the dress.

Step 12:
I decorated the neckline and hem with flowers.

Step 11:
I used this flower model in purple to decorate my dress.

Step 14:
And the hem is decorated with large flowers.

Step 13:
The neckline is decorated with small flowers.

Step 17:
Another way to attach the flowers is using a needle and thread, works fine too!