Well honey bunny it's really very simple. Open your picture in any decent photo editing program (I use PhotoImpression because it came with my computer and I'm too lazy to go buy/download a good program but even MS Paint will work just fine) and then go to the file menu and select Save As. In the Save As Type, select whichever format you need
Hope that helps. If not, just post your pic and I'll change the format for you