I have written an elegy, how to describe subjects in detail? asks about introducing characters who are referenced in an elegy. (The OP asks about writing a preface, though I suspect that's not the best solution.) The question was put on hold as too broad.
An elegy is a particular form; it's not as broad as, say, a novel:
In classical literature an elegy was simply any poem written in the elegiac metre (alternating lines of dactylic hexameter and pentameter) and was not restricted as to subject. Though some classical elegies were laments, many others were love poems. In some modern literatures, such as German, in which the classical elegiac metre has been adapted to the language, the term elegy refers to this metre, rather than to the poem’s content. Thus, Rainer Maria Rilke’s famous Duineser Elegien (Duino Elegies) are not laments; they deal with the poet’s search for spiritual values in an alien universe. But in English literature since the 16th century, an elegy has come to mean a poem of lamentation. It may be written in any metre the poet chooses.
While the article linked there says that some elegies follow no set pattern, the OP has at least written rhyming verse. (The post doesn't specify meter, which doesn't seem especially important for this particular question.)
Given an elegy that refers to other people (beyond the one being elegized), "how do I introduce these people so readers will understand the context?" seems like a pretty clear and focused question to me. What needs to change in this question for it to be reopened?