I just started entering what I know of my family tree using the ancestry.com iPhone app and don't see a place to enter middle names. My inclination is to include them with the first name, but I don't want that to interfere with making connections with other trees. Is there a proper way to enter middle names into family members' profiles?

The trees, whether on-line or in FTM, have no middle name field. I always add it to the first name field and it works out.