Hi,
You can use any of the image editing software such as Photoshop, Image Ready, etc. to place some text. If you don't have one then you can you use Microsoft paint or GIMP (
http://www.gimp.org/ - there is documentation mentioned about GIMP on this link). Feel free to check out how this artist (
http://www.123greetings.com/profile/rashmisaxena/) has taken simple images and put some text around it to convey the message.
For complete documentation of Wiki, check out
http://studio.123greetings.com/wiki/index.php/.
Please let us know if you have any questions,
Best regards,
Studio Team