All about US Emby appointment letter...Is it the letter enclosed in the packet I received?

I really am confused with this letter of appointment to be presented both to St. Luke's and US Emb Manila. I am thinking of it as a letter which US Emby Manila sent me. Am I correct? If not, what is it then? I got preplexed by some postings on the net. I usually read from some of other people's blogs that saint luke's is requiring to bring the appointment letter with them.For now, I am gathering helpful infos before having my Medical Exam. So I shold know what to do.