Q: why don't i see the allow handoff button on my general systems preference?

Hello kristinejoy7,

Welcome to Apple Support Communities! 

I see that you are trying to set up a feature called Continuity on your iPhone and Mac. This is a convenient feature and and I'm happy to assist you with this. 

Please follow the steps in article Use Continuity to connect your iPhone, iPad, iPod touch, and Mac, specifically, these sections:

Before you begin

To use Continuity, check that your iOS device or Mac meets the system requirements for this feature.

 

SMS

With Continuity, all the SMS and MMS text messages that you send and receive on your iPhone can also appear on your Mac, iPad, and iPod touch. You can also reply to your contacts from whichever device is closest to you, including your iPad or Mac.

You can start a conversation in the Messages app or click a phone number in Safari, Contacts, or Calendar.

Set up SMS and MMS with Continuity

1. You need iOS 8 or later on your iOS devices and OS X Yosemite or later on your Mac.
2. Sign in to iMessage with the same Apple ID on your iPhone, your other iOS devices, and your Mac.
3. On your iPhone, go to Settings > Messages > Send & Receive. Add a check to both your phone number and email address. Then go to Settings > Messages > Text Message Forwarding and enable the device or devices that you want to forward messages to.
4. Look for a code on the Mac, iPad, or iPod touch that you enabled. Then enter this verification code on your iPhone.

Set up Handoff

• Check that you're signed in to iCloud with the same Apple ID on all of your devices. 
• Turn on Bluetooth on all of your devices and connect them to the same Wi-Fi network. 
• Make sure that your devices are near each other. 

Use Handoff

1. On one of your devices, open a compatible app, like Mail or Pages.
2. Use the app to start a task, like writing an email or a document.
3. Then you can switch to a different iOS device or Mac. If you switch to a Mac, you can press Command-Tab to pick up where you left off, or you can click the app icon in your Dock:
   
   If you switch to a different iOS device, there are two ways to pick up where you left off:

You can swipe up from the bottom-left edge of the Lock screen, where you see the app’s activity icon  .

 

 

Or if you aren't on the Lock screen, double-click the Home button. On the multitasking screen that appears, tap the banner at the bottom of your screen.
 

Turn off Handoff

If you want to turn off Handoff on your iPhone, iPad, or iPod touch, go to Settings > General > Handoff & Suggested Apps. Then turn off Handoff.

On your Mac, go to System Preferences > General. Then uncheck the Allow Handoff setting.

Have a wonderful day!