The choice of whether to install the 32-bit or 64-bit version of FileMaker depends on a few things (note: this only applies to Windows, there is only one installer for the Mac version of FileMaker):
Is your Operating System 32-bit or 64-bit?
If your Operating System is 32-bit, you will need to install the 32-bit version of FileMaker.
Do you have the 32-bit or 64-bit version of Microsoft Outlook installed?
If you have the 32-bit version of Outlook, you will need the 32-bit version of FileMaker. If you have the 64-bit version of Outlook, you will need the 64-bit version of FileMaker.
Instructions for identifying your version of Outlook can be found on the Microsoft website at What version of Outlook do I have?