1⃣ Put --tile at the end of your prompt.
2⃣ Upscale the image that you like.
3⃣ Download the image.
4⃣ Duplicate the image in a image editor like PS or MS Paint.
Observe how the same image aligns perfectly with itself!
The tile parameter can be used for:
#1 Gift wrappers
Example prompt: cute, cartoon-style teddy bears, child's birthday gift wrap --tile
You can check that each image can indeed be perfectly tiled.