Hey there Rachel,
Thanks for reaching out to us. Typically, you can do a factory reset directly through your settings application on the device. The option for Factory Data Reset can be found by navigating to the Settings application, then selecting Backup & Reset. You should see the option for Factory Data Reset at the bottom there. It will generally make you confirm that this is what you want to do as it will entirely wipe the device.
If you are not able to get into the device at all for any reason, the process is a bit different. If you need those steps, please reach out to us via email at email@example.com and we can get all of that sent to you as soon as possible!