Echo Speaks is a community-developed app by @tonesto7. So you would have to add the code for the app before you can add it using the "Add User app" button on the Apps page of your HE.
You can get the Echo Speaks code from here:
Alternatively, install Hubitat Package Manager (another community-developed app), and use it to install Echo Speaks. Hubitat Package Manager is here:
In either case, be sure to read the Echo Speaks documentation ......
