parents visit visa for uk

[waqas124]

Hi,
i am thinking to apply for my mother visit visa she is in Pakistan.
i have five year visa and my wife and my son is European national living in Uk.
my father works in Saudi Arabia from last 24 years and he is willing to support and pay all necessary travelling and any other cost for her.
while i can provide her with accommodation.
as my mom ties with Pakistan is she have her own house and my other siblings including my 14 years old brother whom she is taking care of.
1.she have certificate form dads company to confirm he is working there
2.his bank saving statement etc
i wanted to know about how to apply and what should i mention in my invitation letter and what my dad should mention in his letter.