how to use Sidecar

For your MacBook year and mode; and your iPad, look at Astropad Standard or Studio versions.

Astropad Standard by Astro HQ

https://apps.apple.com/us/app/astropad-standard/id934510730

Astropad Studio by Astro HQ

https://apps.apple.com/us/app/astropad-studio/id1181582576

See this Apple support article-->Use your iPad as a second display for your Mac with Sidecar - Apple Support

No.

It is not a software issue, but a hardware one

Older Macs do not have nor can incorporate the newest, Metal-capable GPUs.

You want to take advantage of macOS side of Sidecar, you would need to purchase newer hardware.

Sidecar Supported hardware

Sidecar requires Mac with Skylake processors and later models, and iPad models that support Apple Pencil.

Sidecar-supported Mac models:

• MacBook introduced in 2016 or later

• MacBook Air introduced in 2018 or later

• MacBook Pro introduced in 2016 or later

• Mac mini introduced in 2018 or later

• iMac introduced in late 2015 or later

• iMac Pro introduced in 2017 or later

• Mac Pro introduced in 2019

Sidecar-supported iPad models:

• 12.9-inch iPad Pro

• 11-inch iPad Pro

• 10.5-inch iPad Pro

• 9.7-inch iPad Pro

• iPad (6th generation or later) • iPad mini (5th generation)

• iPad Air (3rd generation

Also, what year is your Mac?

Older Macs from early 2015 and earlier cannot run Sidecar.