... or you can try this
To make a seamless dot pattern using jeanniem's embossed dot tutorial:
Make a new image 160 x 80. Fill the background with white. Turn off the background visibility. Make a new transparent layer, name it dots.
Image > Grid > Configure Grid
Make grid 40 x 40
View > Show Grid
View > Snap To Grid
Select Ellipse tool
Check Fixed, make Size > 40 x 40
Make an ellipse in the first grid and make sure it's snapped to the grid, fill with white; drag the active ellipse to the next grid as shown in the image and fill with white. Do the same until you have 4 dots filled with white as in the image.
Turn on the Background layer. You will not be able to see the dots as it's the same color as the dots.
Start jeanniem's tutorial at Step 3 by doing alpha to selection to the dots layer.
Your finished seamless pattern will look like this. Use it to fill any sized layer.