When I try to upload a fritzing file to my instructable its gets uploaded as Arduino SOS.fzz file and not as a picture.What is the correct way of uploading a fritzing file please help.

What you do is you save the file and then you go to the file tab and there will be a choice called "Export". It should be third from the bottom. Then you move over to "as Image" and then choose your file type. You will then need to figure out WHERE you saved it and go through the whole process of uploading it to wherever that may be (Instructables.)
If you want to upload it as an image the you will need to do a screen capture. You can hit the Print Screen button on your Keyboard. This saves the screen as an image in your note pad. Open up MS Paint and hit Ctrl-V to paste the screen shot into paint. Not you can move and resize the image and save it as a JPG.