"Salvation" by Langston Hughes is actually an excerpt from his autobiography, The Big Sea. It describes a religious service within an African American charismatic Christian tradition, in which being "born again" is considered necessary for salvation.
The introduction to your paper should summarize the main point of your paper, which should be Hughes' appropriation of Christian symbolism. The final few sentences of your introduction should be transition sentences pointing forward to what you will cover in the body paragraphs of your paper.
The first body section of your paper should give some historical and theological background to the tradition of tent revivals. It should discuss what would be implied by "being saved" in such a context, and especially the emphasis on personal visionary experience and deep emotional connection to Jesus.
Next, you might discuss color symbolism. The participants in the revival, and Hughes himself, are black; Hughes uses the phrase "jet-black faces" to describe the crowd. The evening outside is dark. The process of salvation, though, is referred to as experiencing light. The children are also referred to as "lambs" in multiple places. In Jewish and Christian iconography, Jesus himself is treated as the equivalent of an unblemished white lamb and church elders and Jesus himself are compared to shepherds tending flocks of sheep (of which the youngest would be lambs). Visually, the lambs are normally portrayed as white. Thus in this passage, we get the sense of conversion to Christianity, even in a black Christian community, as a form of assimilation to whiteness.
The second major body section of your paper could discuss the way the attendees are portrayed as becoming a collective acting as a primal force rather than individuals, as in the sentence: "The whole congregation prayed for me alone, in a mighty wail of moans and voices." Salvation, and the concomitant conversion are symbolized by Hughes' physical situation, initially being part of a group of young people on a bench, then being one of two people, next being alone on the bench, and finally sacrificing his individual will to become part of the collective at the altar.
For your third major section, you might look at sea imagery, as it appears in such phrases as "sea of shouting" and "waves of rejoicing", phrases that evoke the "sea of faith".
Your conclusion could examine the irony that Hughes did in fact experience a conversion at the revival, but it was a conversion to atheism. You might look at what his tears symbolize, both for him (regret for his lie and betrayal of self) and his aunt (the descent of the Holy Ghost). Finally, you might think of this in light of the Gospel of John 11:35, in which Jesus weeps.