Original Source: https://support.wix.com/en/article/wix-editor-uploading-your-own-images
Add your own images to your site to truly make it your own! You can upload images from your computer, social networks, your other Wix sites and using a URL.
Once you have uploaded them to the Media Manager you can use them anywhere on your site.
Your other Wix sites:
(Optional) Select the file and click Add to Page to add it to your site.
When trying to change an image on your site to an SVG file, you will see that the Choose Image button in the Media Manager is greyed out. This is because you cannot replace an image with an SVG file. Instead, you should add the file to your site by following the steps below, or add a vector art and then replace it with your own SVG file.
The images continue uploading even if you close the Media Manager.