The best place to upload most images is Wikimedia Commons, where they become part of a collection that can be used by Wikipedias in multiple languages, as well as our sister projects and the general public.

To upload images to Commons you can use the Commons Upload Wizard tool, which will guide you through the process.

There is an important caveat: Commons accepts only freely licensed images. This means that you cannot upload most images found on the internet, as the vast majority of them are not free.

However, there are some circumstances in which Wikipedia can use non-free or fair use images. This is typically when an image's presence significantly increases readers' understanding of a topic, no free alternative is available, and its use does not negatively affect the commercial interests of its owner. Examples include movie posters, corporate logos, and screenshots of web pages.

To upload a non-free image, use the File Upload Wizard, which will help you add all of the required information. A link to the wizard can be found under "Tools" at the left of the screen.