All Youtube videos I've seen tell me that I go to preferences and select my phone number as one option I can be reached at, but it is not available to me and I'm not sure why. I am signed into my Apple ID and everything but my phone messages and mac messages are still completely separate.
MacBook Air Apple Silicon
I have posted this checklist several times and it has helped some users in your predicament. Each step must be followed and each setting must be correct. Note that you need to have an iPhone for this and most of the settings are configured on the iPhone:
iMessage checklist
iPhone and Mac both logged in to same Apple ID. Try logging off and logging on if necessary.
iPhone Settings => Messages shows iMessage as "on" (sometimes toggling this off and then on fixes some things)
iPhone Settings => Messages shows Send & Receive showing both phone number and email (Apple ID)
iPhone Settings => Messages shows Text Message Forwarding and your Mac is listed and shown as "on" there.
iPhone Settings => Messages shows Send as SMS "on" and MMS Messaging and Group Messaging both "on"
On the Mac: Messages => Preferences shows same and correct Apple ID and "You can be reached for messages at" indicates both phone number and Apple ID (email), and "start new conversations from" indicates the phone number. If this is not the case, you can log out from your Apple ID in Mac Messages and in Mac System Preferences, then log in again to the Apple ID first in System Preferences followed by in Messages.
* Don't see the Text Message Forwarding setting on your iPhone? Go to Settings > Messages, turn off iMessage, turn it back on, tap Send & Receive, tap Use Your Apple ID for iMessage, then sign in with the same Apple ID used on your other devices.
Forward SMS/MMS text messages from your iPhone to your Mac or iPad - Apple Support
I have posted this checklist several times and it has helped some users in your predicament. Each step must be followed and each setting must be correct. Note that you need to have an iPhone for this and most of the settings are configured on the iPhone:
iMessage checklist
iPhone and Mac both logged in to same Apple ID. Try logging off and logging on if necessary.
iPhone Settings => Messages shows iMessage as "on" (sometimes toggling this off and then on fixes some things)
iPhone Settings => Messages shows Send & Receive showing both phone number and email (Apple ID)
iPhone Settings => Messages shows Text Message Forwarding and your Mac is listed and shown as "on" there.
iPhone Settings => Messages shows Send as SMS "on" and MMS Messaging and Group Messaging both "on"
On the Mac: Messages => Preferences shows same and correct Apple ID and "You can be reached for messages at" indicates both phone number and Apple ID (email), and "start new conversations from" indicates the phone number. If this is not the case, you can log out from your Apple ID in Mac Messages and in Mac System Preferences, then log in again to the Apple ID first in System Preferences followed by in Messages.
* Don't see the Text Message Forwarding setting on your iPhone? Go to Settings > Messages, turn off iMessage, turn it back on, tap Send & Receive, tap Use Your Apple ID for iMessage, then sign in with the same Apple ID used on your other devices.
Forward SMS/MMS text messages from your iPhone to your Mac or iPad - Apple Support
Receiving and sending messages from my phone number on my mac.
