‘Po’ is a word used to show respect and humility in the Philippines. It can be used when talking to someone in higher position, someone older, or even when a person in a higher societal status wants to show respect and humble himself before an old beggar.
For foreign people, it’s also appreciated if they include ‘po’ in their statements. For example: ‘Yes’ is ‘oo’ (pronounced as oh-oh), but to sound respectful, people made it ‘opo’. ‘No’ is ‘hindi’, but ‘hindi po’ would be better.
Where to put ‘po’ in the statement depends on the phrase or sentence but if a foreign toungue would use it, it will be better if they will have it at the end of the sentence, like, “I don’t know po”, “I will check your sms later po”, “hello po”, “how are you po” and “happy birthday po”.