The gallery we use does not allow you to link to things on the web. You have to upload images to the gallery from your computer. You can add photos you find on the web to the gallery yourself by doing the following:
When you are on the web and find a picture you want to put in the Gallery, right-click it and a dialogue box will pop up.
There should be a choice there something like, “Save Image As…”. Choose that, and then save the image to your computer, i.e., some place you can find easily. I would make a separate folder on your computer just for these.
Then go to the Media Gallery (see link in top navigation) > Click on the category name where you want to put the picture > Click the link “Add A Picture” > then click the “Browse” button and go find the photo where you saved it on your computer.
Add comment about the image > add a title > and then save.