The first stanza establishes two things: that someone named Felix Randal had died, and the nature of the relationship between Felix Randal and the speaker, a priest. The poem is generally viewed as being autobiographical, with the speaker closely linked to Hopkins—who was in fact a Jesuit priest. (Hopkins changed the surname of the real-life Felix, however—more on that at the end of this analysis!).
The poem opens with a question that seems strangely casual, and perhaps suggests something about how priests are expected to behave. That is, it's not immediately clear that Felix Randal's death has had any major effect on the speaker—as though he is expected to maintain a kind of professional spiritual distance from his flock (his community), and can't make any great display of emotion (though he may feel pain inside).
But the way that the speaker phrases the first part of this question—"Felix Randal the farrier"—hints at the speaker's admiration for the dead young man. This type of description, in which a person's name is linked to something about them (e.g., a particular quality, like "Alexander the Great", or, as in this case, their occupation), is known as an epithet. This epithet conveys a kind of purity—that is, Felix Randal was such a good farrier (a blacksmith that shoes horses), that it's reasonable to define him by his work. That said, this could also be the speaker's way of specifying exactly who it is that has just died—Felix Randal the farrier (as opposed, perhaps, to some other person in his care, e.g., John Smith the tailor).
Though the reader doesn't yet know that Felix Randal was a strong young man, cut down in his prime, the alliteration, consonance, and assonance in this description hint at his impressive physical condition prior to death—"Felix Randal the farrier." Try saying this out loud; there is something noticeably strong, robust and even proud about the sound of these words.