Sometimes the current size of an image isn't exactly what you wanted. Instead of making the image again from scratch, let's resize the image with a few minor adjustments!
STEP ONE
Let's say I have an image that's currently 200px in width and 20px in height.
STEP TWO
I want the width to be 300px. We could go to Image > Image Size and then resize the image, but that will stretch the image and it won't look too good. So let's make a new image with a width of 300 and a height of 20. Drag your original image into this new canvas using the Move Tool and line it up so it's right against the left edge.
STEP THREE
Now zoom in on the right side of the original image. Using the Select tool, select the right end piece.
STEP FOUR
Choose the Move tool and click and hold down on the selected end piece. This will cut the piece that you selected. Take that piece and drag it all the way over to the right and line it up against the right edge.
STEP FIVE
Using the Select tool again, select a piece near the edge where you just cut off.
STEP SIX
Go to Edit > Transform > Scale. The selected box will change a bit and you should see little handles on each corner of the selection as well as in the middle. Click on the middle right selection and drag it over to the right so it meets up with the edge of the corner piece from step 5. Hit enter.
Hit Control + D to deselect. You just resized your image! Go have fun resizing images now!
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