Q: my iphone does not give me the option of "text message forwarding" under setting > messages. i'm trying to activate sms on my phone so that i can send/recieve texts on my mac book air. i need help!

Hello shelbyperry1313,
 

Thank you for participating in the Apple Support Communities. 
 

It sounds like you want to set up text message forwarding but don't have that option under Messages settings. 
 

Be sure to double-check the set up steps mentioned in Use Continuity to connect your iPhone, iPad, iPod touch, and Mac.
 

Your iPhone, iPad, and iPod touch need to use iOS 8.1, and your Mac needs to use OS X Yosemite.

1. Sign in to iMessage on your iPhone, your other iOS devices, and your Mac using the same Apple ID.
2. On your iPhone: Go to Settings > Messages > Send & Receive > You Can Be Reached By, and add a check to both your phone number and email address. Then, go to Settings > Messages > Text Message Forwarding, and enable the device(s) you would like to forward messages to.
3. Your Mac, iPad, or iPod touch will display a code. Enter this code on your iPhone to verify the SMS feature.

Sincerely.