Open your device's settings –> Language and input –> Speech –> Text to speech output.*
Here you can manage settings for speech synthesis (for example, download language pack for offline use) and select another text-to-speech engine.
*The exact way to open TTS settings depends on your Android device
If you don't see the settings, make sure you have installed TTS on your device. If you disabled TTS engine, enable it first: open device's settings –> Apps –> Disabled –> Select your TTS (for example, Google Text-to-Speech Engine) and press Enable.