In order to send an SMS message to specific contact, navigate to Contacts and click on the contact you would like to send an SMS to.
In their profile card, you will see the Message button.
Click on it and select Send SMS
Write your message and click Send Message.
How to send a test message
If you would like to send a test message to make sure it looks good when received as an SMS, simply click on Send Test, the SMS will be sent to the test number you've set up in your Twilio account.
How to schedule an SMS to be sent later or a specific date and time
Once your SMS message tab is open and you're done writing your message, click on the Schedule button and select your desired date and time and click Save Message.