It's always good to check the manuals first. I'm attaching one for your convenience.
SQL passwords must be changed on the DB server (ask your DBA)
BSM Installation Guide Appendix 3: Server Deployment and Setting Database Parameters
For information on assigning a Windows user to run the BSM service, see "Changing BSM Service Users" on page 81. For information on adding a Windows user to MS SQL Server, see "Using Windows Authentication to Access Microsoft SQL Server Databases" in the BSM Database Guide