As a Google Workspace School, we make use of Google Photos for some of our creative subjects.
It is available online using the App Switcher Menu from any Google Web App.
Mobile Apps
There are also dedicated apps for iOS / iPad OS and Android devices.
Please avoid enabling automatic backup of photos when installing on your mobile. As this will eat up your storage very quickly. We've put together instructions for iOS / iPad OS and Android.
Desktop Apps
Google offers apps for the desktop as well. These are not necessary over the functionality of the web version.
https://photos.google.com/apps
Uploading Photos through the Web
When you first open Google Photos the screen will look like this.
You can use the 'Upload' button in the top-right to add photos and/or videos. This will allow you browse your local device and upload the files you need.