This is how to enter Developer Mode on Android TV. The steps taken are pretty much the same as how to enter Development Mode on most all other Android Devices.
**REMEMBER: It's a good idea to revert back to pre-developer options after testing such as turning OFF "Verify Apps from Unknown Sources" and "ADB Debugging." This is especially true if this is your personal device and/or you will be doing a lot of web browsing on this device. Malware or MITM attacks can target pretty much anything these days and many people wouldn't think of a TV as an attack vector.
Device Specifics:
Sony Bravia - XBR75x940C
Android Version - 5.1.1 Lollipop
