how should I be positive about financial support?
Depending upon the university, your funding may come from the department, rather than the university, and it thus would likely be the department's responsibility to send you a letter outlining where your funding comes from. (In some cases, this devolves to the faculty member.)

If you have any questions, the best place to start would be the graduate advisor or the graduate admissions officer for your program. They should know how funding letters are announced.