Photoshop file sizing is handled under the “Image” menu item:
Once you select Image, select “Image Size”. Set up the parameters in the pop-up box as shown below.
You will now have to save-as, and rename your file. DON’T overwrite the original!
In Photoshop the equivalent of a Lightroom preset is called an “Action”. Actions are essentially just a recording of the steps you go through between the time you start the recording and end it.
This is how you would record this action. (1) Make sure your action window is shown in the right bar of the photoshop window. (select Window/Actions in top menu…see the actions pop-up in the right bar)
Now begin your recording by clicking on the small folded page icon at the bottom of the actions pop up window. Make sure to put that recording into a subcategory you can find later since there are a lot of pre-set actions there already.
Follow the steps described above to reduce file size (don’t go through the save step, as the action will just wright over whatever is there…then click the the little “box” in the actions panel to stop the recording. When you want to play the recording in the future simply close the play (arrow-triangle) in that same panel.