how do I update the software on my macbook

Hello, thanks for reaching out to Apple communities!

If you mac can still receive MacOS updates, you should be able to install a new update by following these steps...

1. Click the Apple logo on the top left of your screen
2. Click system preferences
3. Click software update
4. Look to see if you have an update available
5. If you see an update click on update then wait for it to install!

If you don't see an install this could be 1 out of 3 things.

1. Your mac is already fully up to date
2. Your mac can no longer receive updates due to your machine being too old (Let me know if you want help figuring that out)
3. Your mac is not connected to the internet

If this does not solve your problem let me know!

I am sure I can help further!

Cheers!

The Age of this computer will Govern what newer version of macOS it will Qualify to install. Use About this Mac from the Apple Icon on Desktop - the required Information will be there.

With the above information in-hand - follow this How to get old versions of macOS and verify what version this computer Qualifies to install.  For Best results use Safari to commence the download as Others may not work.

Safari will open a redirect and open the Apple Store where the download can commence

Tips Big Sir Upgrade Released Nov 2020

Tips Monterey Upgrade  Released Oct 25, 2021

Make Time Machine Backup  is very useful and can be used to Revert to Previous Working macOS

Notation - Mojave is the Last version to support 32 bit applications / extensions and Drivers. Catalina, Big Sur & Monterey supports only 64 bit and there is no workaround.

Suggest using Go64 to find 32 bit application before attempting the upGrade. Some or many of the Application already installed may required update or upGrades to 64 Bit Versions.

Are there any AntiVirus, Disk Cleaner, Optimizers, Un-installers, etc installed which should be removed as per Developers Instructions. They are useless, unneeded, cause havoc and interfere with the normal  operation of the OS and may even Corrupt the OS requiring a Reinstallation