hey
gmail uses ‘labels’ not folders such as hotmail or yahoo do
log on your account
go to ’settings’
‘filters’
create a filter called ‘facebook’
then clic on ‘filters’
go to the ‘facebook’ filter
click on ‘next step’
on “Choose action – Now, select the action you’d like to take on messages that match the criteria you specified.
When a message arrives that matches the search: from:FACEBOOK, do the following…”
select ‘apply the label’
scroll down and tick ‘facebook’
click on ‘update filter’
hope I helped
seeya☺