Now you're ready to apply your recorded batch process to a folder full of your images. Click on the File menu, move down to Automate, and select Batch from the sub-menu.
The batch processing dialogue window is quite complex, and offers a great many options. First, you have to tell it where to find the photos on which you want to perform the batch process. You can have it just use files that are already open, import them from another source such as a scanner, or more usually to find them in a folder on your hard drive.
If your recorded action includes an instruction to open a file, you'll need to check the box labelled Override Action "Open" Commands, otherwise it will simply try to perform the action on the same file over and over again, causing an error.
Similarly, you'll need to specify and output folder. This should be a different folder than the source folder, otherwise Photoshop will attempt to over-write your original images. Again, if your process includes a Save action (it does in this case) check the box labelled Override Action "Save As" Commands. Doing this ensures that all the images will be saved into the specified folder only, at the quality setting you specified earlier. You can also specify a name for your re-sized images, and a number which is assigned automatically.
You are now ready to begin your batch process. As soon as you click OK it will start, and Photoshop will then continue to process your images until it has completed all of the pictures in your specified source folder. Depending on the speed of your computer and the size of the source images this could take a while, so go off and make a cup of tea or something.
You can also use this process to create thumbnails, by simply changing the size to 100 x 100, or whatever size you need. It is worth noting however that resizing in this way only changes the width of the image to the specified size, so a vertical format image will come out measuring 600 x 800 pixels. If you want all your pictures the same size you will have to set them all to the same orientation.