To turn on vibrate on your iPhone, go to Settings → Sounds & Haptics. Toggle Vibrate on Ring and Vibrate on Silent to enable vibration. You can also use the Ring/Silent switch on the side to quickly activate vibrate mode.
To turn on vibrate on an iPhone, go to Settings > Sounds & Haptics. Enable Vibrate on Ring and Vibrate on Silent depending on when you want vibration. You can also adjust haptic feedback strength here. Once enabled, your iPhone will vibrate for calls, alerts, and notifications.
Go to Settings > Sounds & Haptics. Make sure the Play Haptics in Ring Mode and Play Haptics in Silent Mode are toggled on for overall vibration. Tap the alert, tap Haptics, and choose a vibration pattern other than "None" for particular alerts (such as Ringtone or Text Tone).