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?