how do i open my macbook air (M1) if i have forgotten my account and password

Verbatim from the site provided

Reset your password

If you don't remember your password, or it isn't working, you might be able to reset it using one of the methods described below. But first try these simpler solutions:

• Make sure that you're typing the correct uppercase or lowercase characters. If your keyboard has Caps Lock turned on, the password field shows a Caps Lock symbol .
• If the password field shows a question mark, click it to display a password hint that might help you to remember.
• Try to log in without a password. If that works, you can then add a password by following the steps to change your password.
• Try to log in with the Apple ID password that you use for iCloud. If you just changed that password and the new password isn't working, try the old password first. If that works, you should be able to use the new password from then on.

Change or reset the password of a macOS user account

Recovery Mode is your next best bet

You'll need to boot your Mac into Recovery Mode in order to access the password reset tool. I've found the easiest way to do that is to start by turning your Mac off.  

The trick to getting into Recovery Mode will depend on the kind of Mac you have. For Macs with an Intel processor, press and hold the Command and R keys on your keyboard, then press the power button. Hold in Command+R until you see a progress bar show up below the Apple logo. You can also get into Recovery Mode by restarting your Mac and trying to time the keyboard combo of Command+R, but in my experience, starting with your Mac turned off is the most reliable method. 

For the recently released Macbook Air, MacBook Pro and Mac Mini that use Apple's M1 processor, you'll need to turn off the computer and then press and hold the power button until you're presented with an options button. Click it and then select Recovery. (We have a more thorough walkthrough of Recovery Mode on the M1 Macs.) 

With your Mac now in Recovery Mode, click on Utilities in the menu bar followed byTerminal. A new window will show up, waiting for you to enter a command. Type "resetpassword" as one word, without the quotes, and press Return. 

Close the Terminal window, where you will then find the Reset Password tool. Follow the prompts, which include signing in with your Apple ID and then selecting the user account you need to change the password for. 

Brian - That is very good and pleased if is now sorted. Ah, the old space in account issue.

Most important, one can now use the newest toy.

For the Purposes of Assisting Others with Similar issue as your - What was the Method used to resolve your issue. Others on the Community might be searching for a similar answer.

Recovery Mode is your next best bet

You'll need to boot your Mac into Recovery Mode in order to access the password reset tool. I've found the easiest way to do that is to start by turning your Mac off.  

The trick to getting into Recovery Mode will depend on the kind of Mac you have. For Macs with an Intel processor, press and hold the Command and R keys on your keyboard, then press the power button. Hold in Command+R until you see a progress bar show up below the Apple logo. You can also get into Recovery Mode by restarting your Mac and trying to time the keyboard combo of Command+R, but in my experience, starting with your Mac turned off is the most reliable method. 

For the recently released Macbook Air, MacBook Pro and Mac Mini that use Apple's M1 processor, you'll need to turn off the computer and then press and hold the power button until you're presented with an options button. Click it and then select Recovery. (We have a more thorough walkthrough of Recovery Mode on the M1 Macs.) 

With your Mac now in Recovery Mode, click on Utilities in the menu bar followed byTerminal. A new window will show up, waiting for you to enter a command. Type "resetpassword" as one word, without the quotes, and press Return. 

Close the Terminal window, where you will then find the Reset Password tool. Follow the prompts, which include signing in with your Apple ID and then selecting the user account you need to change the password for. 

Check again - a possible solution was provided at 5:00 PM and just above your post.

https://support.apple.com/en-us/HT202860

Welcome and Thank you too !

Do come back to these Forums if / when additional Assistance is needed. There are many Contributors willing to help

I don't know how to do this and I need step by step help

I need help resetting my password that I have forgotten. Not very good with this kind of problem so will need step by step help.