Here's how you can add cool effects and textures to your designs to give it the perfect finish you are looking for:
Decide what kind of effect you would like to work with based on the tones and type of images you are working with. Let's look at dirt, as I would like to texturize the background of my image.
Once you are happy with your selection, add it to your canvas.
Here's what I went for -
Scale the effect according to your preference. You can also make adjustments to the appearance of it by clicking on image adjustments on the right panel of your screen.
And we are done!