Ignorant question

I am new to this whole thing. I am trying to add a template design to my phpbb forums. My question is, on my FTP program, it asks for IP/Host #1 Which IP address are they looking for? Where can I find it? Which Host are they refering to? My phpbb host? or my site builder host? I am hoping the rest will beunderstandable, once I figure out where I am at, and which usernames and passwords to put in. thank you for your time and patience