there are many ways but here are 3 of them (provided that you are using a1111) https://stable-diffusion-art.com/controlnet-upscale
For the SDXL 1.0, my old scripts does not seem to work for upscale feature.
For example i had "tile resample" model, while using "Ultimate SD Upscale" script. It used to be working before with SD models of 1.5.
But with SDXL 1.0, I dont know which file to download and put to what path ? Can anybody help ?