Using the application is as easy as having a tab open with the photo you want to edit, clicking on the icon located to the right of the address bar, and step by step, applying any of the many effects that you want. From basic things such as cropping, resizing, rotating, etcetera, to more advanced effects similar to those of Instagram, such as frames, texture, and all kinds of other additions.
The best of all is that using any of these effects is as easy as the click of your mouse. If you like the result, you can save the changes, and if not, you simply cancel them and try something else (there's enough to keep you busy). Once you are done, all you have to do is save the image.
PicMonkey is a very complete photo editing tool that, beyond having everything you need to edit your photo just how you want it, allows you to do it online and with impressive ease.