Just a few step u can make your text on fire effect..
First step create a new layer or your can use a shortcut key as ctrl+n set color mode as grayscale then filled background color with black

Use a text tool, type in the word u want with the white color.

Adjust the location of the text u want,then go Layer>>Merge Layers
After Merge layers go Image>Image Rotation>90cw

Then go Filter>>Stylize>>Wind>Method Wind>>set the direction from the left and you can set more wind effect click  ctrl+f

After set the wind method wind rotate back go Image Rotation>90ccw

After rotate back go Filter choose Distort> Ripple make the floating flame up

After make the effect go Image>Mode>Indexed color

Then go Image>Mode>Color Table select Black Body

The last step go image mode agian select the RGB color
Now is complete enjoy ^^