This is a really basic tutorial on how to add a simple overlay and font to a photo using Photoshop. Please note: I'm using Photoshop CS6 on the walkthrough below but the principles are the same on any version
1. Open an image in Photoshop
2. Create a New Layer. Select Layer from the menu, then New then Layer. Give your layer a name, in this case I called mine 'Black Box' because that's what I want to put in the layer I'm creating. Then click OK.
3. Creating a Box overlay. Select the Rectangle tool, as shown below and chose the colour you would like the box to be.
nb: you could also select the Ellipse, Polygon, Line or Custom Shape tools from here too
4. Now create the box. Left click on your image and drag to make a box shape, to ensure a perfect square (or a perfect circle if using Ellipse shape tool) hold down the Shift key. Position the box where you want it using the move icon (shown below).
Now if you like you can change the opacity of the box, as I have. Simply adjust the Opacity slider in the Layers Window on the right hand side of the screen. If the Layers window doesn't apear you can select it to appear from the top menu - Window - Layers.
5. Adding text. First things first, create a new Layer, as you did in Step 2, this time call it 'Text'. Now using the Text Tool (the T icon) click anywhere on your image and start typing. You can drag the text to where you want it at anytime using the Move tool (the arrow icon at the top of the left hand icons menu).
Now I have my text where I want it I would like to align it centrally. In the pink box below you'll see how to align text left, center and right. I clicked the center one for my example.
Now with my text aligned I need to re-size it to fit my box. Below shows you where to adjust your font size.
And job done!