The description says that I need to "move the mouse to overlap the focus circle on the corresponding piece of clothing."

However, the focus circle only appears at the start for me and then goes away for the rest of the game by falling off the right edge of the phone.

Right now, things seem a bit too confusing. Maybe in the next version, keeping the arrow in the green section for longer should progress the green bar at the top? That makes sense from a game design standpoint.

Sorry if the instructions are not very clear. I think I understand what the problem is. The clothes are unlocked in a certain order, the active piece has a small circle that indicates where you must move the large circle to unlock clothes. Once unlocked a piece of clothing, another small circle and another large circle will appear. While you try to overlap the large circle on the piece of clothing, you should try to keep the indicator on the green section of the curved bar.

Does the large circle disappear forever for you? If so that's a bug, the circle should follow your mouse, and move faster the farther it is from your cursor. 

I am working on an overhaul to this mechanic, which should be out in a week or two.