Hey Jeff, welcome to SmattThings from IRIS. In SmartThings, Device Handlers are used to connect devices with the hub while SmartApps are used to implement specific use cases using devices connected with SmartThings.
To connect your keypad with SmartThings you only need this device handler and you should be able to access and configure your keypad through the ST mobile app after pairing it.
Depending on how you want to use the keypad, you will need SmartApps. There are a couple of examples outlined by RBoy above which talk using the keypad to arm and disarm your security setup.
If you take a look at the first post it will give you more example of how you can use the keypad for different use cases like controlling garage doors, patio doors, acting as a second lock, a security keypad etc. It also outlines many of the popular and feature rich SmartApps which can make the most use of this device handler and the keypads.
Hope this helps