If you have a whole folder you want Watermarked, proceed to the File Menu and
choose Automate > Batch.
In the resulting dialog is divided into four sections: Play, Source, Destination and Errors.
In the Play section pull down "Action" and select the Action you just created.
In the Source section, click the 'Choose' button and highlight the folder of files you want watermarked. (Hopefully you copied the folder, and will actually be watermarking copies of your files!)
In the Destination section choose "Save and Close"
If you wish to move the newly copied files to a new folder, click Choose... and find the folder.
Are you ready? Click "OK" and sit back. Have coffee. When you get back, your files
will be watermarked.
taken from -
if i can ask you really quick what version of photoshop are you running?