Create realistic Forests for regional Maps in Photoshop

[TempyTheCleric]

So i can create the "texture?" not a problem but then i get lost and i have no idea how to do or what any of the below means....

And done! This is the structure you can now use for the forests! How do you paint them?
Easy:
Create a layer with mode "overlay" and add the texture as a smartobject and cut mask.

I'm just having a hard time figuring this out and i have been trying to for a few hours now so help someone please!

[Revock]

You hold control key and click on each of the layers you want in the smart object in the layers tab to select multiple layers then, * in CS2* creating smart objects is under "Layer"-->"Smart Objects"-->"Group into New Smart Object" If you have a newer version of PS i wouldn't know but its probably similar. Then with the smart-object above the overlay layer, select the smart-object layer, "Layer"--> "Create Clipping Mask".