It's pretty simple to put text into images using PhotoShop. The majority of the tools are the same but here are the example using CS3 (I believe the layout changed from 2 columns to 1 when Adobe introduced the CS version.. but it's been a while since I used 7 so I'm not 100% sure)
To put in text, just follow the steps:
1. Select the T from the left toolbar (Type Tool)
2. Select the Font / Size etc from the top toolbar
3. Select the color from Swatches (default is Black)
4. Mouse over the image where you want to put the text and left mouse click
There you have it.