Specifically for running existing applications without the overhead of development tools.
You will see a list of files. Select the one that matches your architecture (usually WINDOWS.X64_19c_client.zip for modern Windows servers). download oracle client 19c
If you don't need full admin tools, consider + SQL*Plus package (still lightweight but missing exp/imp, SQL*Loader, etc.) download oracle client 19c
Click the "Accept License Agreement" radio button at the top of the download list. download oracle client 19c