Option 1: edit them locally on your computer. How this works depends on your operating system. For many, there are image editing tools that enable mass editing. As soon as this is complete, upload the edited images to WordPress.
Option 2: upload the images to WordPress as they are in the original. Integrate them into your site and leave it up to your theme how they are displayed in the frontend. Depending on how you integrate them into the page, you can also influence the size if necessary. WordPress automatically generates the required sizes at the request of the theme or your settings.
My advice would be to use option 2, as the images are then also generated as thumbnails for different viewports.
