how do i upgrade to macOS Catalina 10.15?

The following may help: How to get old versions of macOS - Apple Support

Note that you did not post what model and model year of Mac that you wan't to upgrade to Catalina so be aware that yours may or may not be compatible with Catalina.

❗️ Do NOT upgrade until you have made a Time Machine or other backup of your startup drive.

Learn How to Back up your Mac with Time Machine

How to Upgrade  macOS:

The macOS version you can upgrade to depends on the year your Mac was released.

Click the  (Apple) menu at the top of your screen and choose About This Mac.

Check the Compatibility of your Mac with newer versions of macOS:

➡️ macOS 10.15 Catalina is compatible with the Macs listed here

❗️ – IMPORTANT – Your 32-bit apps won’t work in Catalina, Big Sur or Monterey.

https://support.apple.com/en-us/HT208436

Use the free utility Go64 to check the compatibility of your apps:

https://www.stclairsoft.com/Go64/

✅ - IF your Mac and apps are compatible, then using Safari only, download the macOS upgrade installer app:

Click > Catalina.

Once downloaded, double-click the “Install macOS…” app in the Applications folder to begin the upgrade.

michelle206, I spent a big chunk of yesterday struggling with the same thing. After upwards of an hour online with Apple Support I was advised to take 2 aspirin and try again in the morning.

I haven't tested the install just yet, but I did perhaps find an end-around in being able to download the Catalina Installer though a post at OSXDaily which pointed to a solution offered by dosdude1. Seems pretty straightforward in the d/l plus creating a boot drive and .iso images. Crossing my fingers on the install.

Really struggling to open the Catalina download link... it simply wont open and displays a blank page? Any ideas please?