MacBook Pro OS X

Hey!

This should help:

Make sure that you have an active internet connection.

Restart your Mac computer.

Close all apps that are open.

Make sure you have enough storage on your Mac.

Then,

Download macOS Catalina

Or use this link to open the macOS Catalina page on the App Store: Get macOS Catalina. Then click the Get button or iCloud download icon.

Also see: https://support.apple.com/en-us/HT201475

Thank you.

First, see How to upgrade to macOS Catalina. The fourth section has the download link at the end of the section.

Before You Upgrade macOS

1. Fix any problems before upgrading.
2. Run First Aid in Disk Utility while booted from your Recovery HD.
3. Backup. Make a bootable clone using CarbonCopy Cloner or use TimeMachine.
4. Be sure your startup disk has 18-20GB of free space during the installation.
5. Upgrade third-party software for compatibility. See App Compatibility Table - RoaringApps. If you have mission critical software, then DO NOT upgrade until you know that software is compatible with the version of macOS you are about to install.
6. Disconnect all third-party peripherals.
7. Download the installer which will be in the Applications folder. Quit the installer after it opens, then make a copy of the installer and save it in the Downloads folder. The one in the Applications folder will be deleted after a successful installation.
8. The download is large, anywhere between 5 and 9GBs. It takes time to complete. Be patient.
9. Double-click on the installer in the Applications folder. Click on the start button to begin the installation.