How to Make a Custom Brush in Photoshop
In Photoshop: Create a new photoshop document by clicking File, New. Change the Height and width to 1000 pixels each. Set your background to white.
When your document opens, type/create what you want your brush to be. (www.shannonmariephotography.net or ©shannonmariephotography)
Create the brush: Edit, Define Brush Preset. Name your brush. Close the document (no need to save).
To use this brush, open a document or a photo. Create a new layer. Find your custom brush in the brush pull down menu. Click where you want it to be. You can change color, size, opacity, etc… Make sure to "merge visible layers" before save as. When I am saving an image with my watermark, I just add the © symbol to the end of the img # (101414_5555©.jpg). This helps me stay organized and easily know which file to use when uploading, etc...