When you create a gallery in a project, by default, the gallery has the same name as the project. You can always edit the gallery name later, here's how.
If you don't know how to create a gallery, you can learn how, here.
To change the name of your gallery, open up the project with the gallery. Scroll down to the gallery section and click "Edit Gallery".
Project > Edit Gallery
After going to the editing page, go to the gallery settings tab. The gallery name will be the first text field on the top of the page.
Type your new gallery name, and click "Save" at the bottom of the page. That's all there is to it! Now your gallery has been renamed.