We have a plugin that can provide a photo gallery on your site. The plugin will create the thumbnail for your images and give you options to place the galleries on pages or in widget areas. Keep in mind you still need to optimize your images for websites. So it is best to first save your images to a folder on your computer and keep the images at 72ppi and no larger than 1080x720px. There is an option when importing the graphics that you can check to optimize images and will scale images to max width 800px or max height 600px.
Below is an example of a gallery placed into a page.