Ok, since you asked ME, I'll help..

Open your image first.

Action is a tab in the History box, normally the middle box along the right side of Photoshop. Click the tab and you'll see "Default Action" or something... Click the "New Action" button which is a little piece of paper with the bottom left corner peeled up (next to a record, play and stop button. This is all in the action box). Click that and name it something like "Resize". Then you'll see a drop down menu labeled "function key", pick a key from the list, that key will start the action. Click Ok. Now you'll see it highlighted in the box, click the record button (the circle). Now go to image, image resize and do whatever you will be doing repeatedly. It's also a good idea to click File>Save and click the okay button, as this will be repeated also.