If you are and just want to update specifically to 10.15.2, you can use the standalone installer.
: You must already have an earlier version of macOS Catalina installed to use this specific package. System Requirements Before installing, ensure your Mac is compatible: macOS Catalina - App Store macOS Catalina 10.15.2 Free Download
: The installer (roughly 8 GB) will download to your Applications folder as "Install macOS Catalina". If you are and just want to update specifically to 10
: macOS Catalina 10.15.2 Combo Update from Apple Support. File Size : Approximately 4.59 GB . macOS Catalina 10.15.2 Free Download
: Visit the official macOS Catalina page on the Mac App Store .
: Click the Get or Download button. This will often open the "Software Update" pane in System Preferences.