Just made this simple tutorial for adding a text in your picture, using Photoshop software.
You can either add a text with the TEXT Tool or you can draw it manually using the brush.
The Opacity option works lovely in making the texts (or any layer in fact) as transparent as you want to.
Remember to SAVE your working PS file (.psd) and to save one image with "SAVE AS" for making a file .jpg or .png or whatever you need :)
Simple, but hopefully something useful :)