I think to do what you are trying to accomplish, you will need to specify your CSS code for each fieldset on the basis of their id (which can only be detemined by examining the code generated in the publish tab for your form). As an example:
#tfa_PersonalDetails { float: left !important; }
#tfa_EmploymentDetail{ float: right !important; }
etc.
Please let us know if you have further questions, FA Support.