To clone, you drag the loupe that appears on the screen to set a source point—the point from which you want to copy. Then select the brush, and drag where you want to copy to. For as long as you're dragging, the source will move relative to its initial position in the same way you move your finger. When you release and begin dragging again, the source will be reset to the position under the loupe.
This video shows cloning on iPad, but it works in exactly the same way on iPhone
Curves are a way to alter the brightness and contrast of an image. Curves work somewhat similarly to the equalizer on a sound system (A more accurate analogy would be to a dynamics processor). However, instead of making bass sounds or treble sounds relatively louder or softer, with curves you can make the dark areas or light areas darker or lighter. In this way you can increase or decrease contrast, and control in a sense where that contrast occurs.
From left to right, the curves graph goes from dark to bright, just as the equalizer goes from bass to treble. However unlike the equalizer, the vertical component of the graph also goes from dark to light, rather than quiet to loud. This is why the base line of the curves is diagonal. The bottom left point means that "pixels which are initially black (are on the left) will remain black (on the bottom)". The top right point similarly means that "pixels which are initially white (on the right) will remain white (on the top)".
Similarly the center point from left to right starts as the center point from bottom to top. If you pull this center point up, it means pixels originally of medium brightness (center left to right) will in the resulting image be brighter, since they are now higher from the center from bottom to top. In this manner, the curves displayed at the beginning of this segment show an image in which the shadows are lightened in order to reveal shadow detail, whereas the bright areas of the image remain mostly unchanged. Everything of less than middling brightness in the resulting image will be brighter than it was originally.
Filterstorm's curves work fairly similarly to most other curves with a few differences. On many desktop programs, clicking somewhere on the curve without a point will add a new point. Due to the imprecise nature of fingers, this is not true in Filterstorm. When you place your finger down on the curve control, Filterstorm determines which point is closest to your finger. When you slide your finger, it moves that point. If you wish to add a new point to the curve, tap the "add point" button, then your next tap will create a new point under your finger.
The text tool is in Filterstorm is not unlike that in many other applications. You can set the text, color, size, font, and alignment in the controls. What is different is that the size and position can be altered from the controls, but also by pinching to zoom, and moving of the image on which the text is to be situated. This can make it very easy to place text where you want it very quickly. You can also rotate text by using a two-finger rotation gesture.