What you said is not very clear, so I don't know if you uploaded it online. When you make your photos on a computer, the size or resolution of your photos may be large, but after you upload them to a website, the website may automatically compress them for you (because all websites require small-size pictures to prevent traffic congestion). Therefore, it is suggested to set your photos on the computer to the size required by the website, so that the website will not automatically compress your photos after uploading.

If you see your photos blurred in the "print preview" in the software, it doesn't matter, because that's just a way to reduce the display of the whole page, and the printed ones are still clear.