If you're viewing a web page (in any browser), simply right-clicking on an image should provide you with an option to save that image to your hard drive. (The image will be in whatever format it was when the page was created. That's most likely to be jpeg but it could also be png, or similar).
If the creator of the web page has disabled the right-click functionality, you can still save the image by saving the entire page. (Press Ctrl and S together). That results in you getting one 'index' file for the page (containing the instructions for compiling it), together with a folder which contains all of its component files, including the image you want.
Alternatively you can simply capture a screenshot of the relevant part of the page by using the Windows Snipping Tool (or Snip & Sketch) or by using the screenshot facility that's built into some browsers, ensuring that you select 'jpeg' as the file format when you sae the screenshot to your hard drive.