(Watch from 1:52 to see the zbrush installation steps in action.)
Step 1: Find a brush you like, and choose the Zbrush option to download
Step 2: Locate your Zbrushes folder - typically C:/Program Files/Pixologic/Zbrush 4R8/Zbrushes
Step 3: Create a new subfolder there, and call it 'Fabric'
Step 4: Move the ZBP file to that folder
Step 5: Restart Zbrush
Step 6: In the lightbox go to Brushes and you should see a subfolder with the brush located in it
Step 7: Select the brush by double clicking on it, and drag out on your mesh
Step 1: Enter into Sculpt mode
Step 2: In the toolbar (T), Add a New Texture
Step 3: In the texture properties, click Open Image
Step 4: Locate your alpha brush and click Open.
Step 5: In the toolbar, change the stroke method to Anchored
Step 6: Click and drag the brush onto your mesh, and you should see the folds appear.
Bonus: Painting Fabric Seams with Substance Designer + Painter
While you can paint seams in your sculpting software, it's actually best to use Substance Painter. Why? Because not only will the detail be much sharper and a higher resolution - as you're painting directly to a normal and therefore aren't limited by polys - but you'll also be able to simultaneously paint a mask for the stitching, so you can later change the color. Very cool!
There are quite a few steps involved, but the payoff of having accurate, sharp seams is worth it!
Third Party Tutorials
This tutorial is for creating preset brush libraries within Cinema 4D. Note that Poliigon brushes must be inverted and saved in an application like Photoshop, in order for the depth information to function correctly within Cinema 4D.