the Pay Later option was added with version 2.2.0. We\'re now at 2.2.2 so what you are using is very old and lacks many of the newer features. To get Pay Later, you simply need to upgrade. Login to your account and download it.
For ECheck, you need to enable this on your authorize.net account. It will be an added monthly cost, but once you add that on your account, you can use that in DT Register.