Sorry friends I had already finished the first petal by the time I realized that I had to explain the steps.
There are six vertical lines in a petal.we should move the needle under the lines without piercing the cloth.
so first we move under lines 1,3,5.
Then turn around the cloth and move under lines 2,4,6.Continue till the outermost lines are filled.
Now move alternatively between remaining four lines.That is first under 2,4.Then under 3,5. Continue till only centre most lines are left out.
Now move under these two lines to fill them.