1. Open a new document
2. Typ your text
3. Open the blending options (fx) and choose Bevel & Emboss
In this screen you can manage size, depth and your shadows and highlights and the angle of the light. Just try things out to see what works best for your pattern
4. Click on Textures under Bevel & Emboss and choose a pattern
Now we got the pattern into the text
5. Now we need the color the pattern. To this choose Pattern Overlay and choose the same pattern.
Now we have our pattern in the text.
Set the same scale in Text overlay and Pattern overlay (or choose in both screens for Snap to origin)
Easy quick and simple !
You can also define your own pattern.
Make a picture of it.
Open it in Photoshop.
Cmd A to select all (Ctrl A in Windows)
Go to Edit > Define Pattern
Give it a name and save it.