WUFI

As an assignment my prof wants u to compare three kinds of wall. I am supposed to set "the actual indoor and outdoor air pressure difference is about 5 Pa, and you can assume the air leakage rate as 0.3 L/s.m2", but I don't know where I should set in software (WUFI pro).
Could you please help me?

in WUFI Pro (and also in WUFI Plus) you can set 'Sources, Sinks' in the assembly edit form. There you can select and put a air change source in the assembly. You can fine more information about this if you search for 'air change source' in the WUFI Pro help.