If you are using Filemaker on WIndows, select the "enlarge window contents to improve readability" option in Preferences.
Thanks for that Phil, I forgot to disclose that I a on an IMac usin OS X
I don't think mac systems offer that preference setting.
I think you would need to decrease your monitor resolution to get larger print in the dialogs/menus, etc.
On the Mac:
option-cmd 8 toggles zoom on and off
option-cmd = zooms in
option-cmd - zooms out
Check out System Preferences>Accessibility for more settings