How do I send text messages (NOT iMessages) from my Mac?
Yes, it is possible! However, you do need to set things up first. 

Follow these steps:


Sign into iCloud on your Mac and iPhone using the same Apple ID
On your Mac open the Messages app
On your iPhone go to Settings > Messages > Text Messages Forwarding
You should now see your Mac listed - tap on the toggle to enable it. 
You’ll see a prompt asking you to enter the code shown on your Mac. 
Enter the code


Now when you add a non-iPhone mobile number into Messages on the Mac it will be highlighted in green - this is an indicator that you are sending a text message and not an iMessage.

NOTE: As all text messages sent from your Mac are now forwarded via your iPhone, they will count towards any associated costs for your mobile plan (if any).