So there are a few different ways to achieve this effect but I’m going to show you the easiest way, at least in my opinion.
First, find an image you like.
Next, duplicate this layer. (Right-click your background layer and hit duplicate, or go to Layer > Duplicate)
Here is the whole flower:
Pretty cool huh?
You could leave it just like that, or you can experiment with adding more color. Here are some variations:
I decided I didn’t like her lips or shirt strap colored so I just hit the undo button a few times to get rid of it.
I thought it would be fun to make her eye pop. So, I took my paintbrush, lowered the opacity to about 15%, and colored in her eye.
Finally, you could add a funky border: (I also added strokes and inner shadows
to achieve this look)