Go to a website that provides high-definition pictures. Find the high-definition pictures you need. High-definition pictures have various applications. Different formats, different categories. There are landscape pictures, people pictures, and the formats of pictures are jpg, bmp, png, tif, gif and so on. There are many more, so I won't list them one by one.
Different formats have different pixel sizes. The capacity is also different.
So, after finding high-definition pictures. You can save it as and download it to your computer. It can also be downloaded to the computer through various download tools.
I hope I can help you.