Quoting the article
Modify the ODBC System DSNs (bes_BFEnterprise, bes_EnterpriseServer, enterprise_setup, and LocalBESReportingServer) to point to the new SQL server instance. This modification will allow you to avoid re-installing the BigFix Server application.
*Use ODBC connection wizard to test connection
*For 64-bit Windows systems, use the 32-bit version of the ODBC tool (C:\Windows\SysWOW64\odbcad32.exe) to configure the System DSNs.
These days I believe you’d use both the 32- and 64-bit odbcad32.exe programs to update both DSNs