"We grow accustomed to the Dark" is a poem written by Emily Dickinson. In this poem, the poet writes about how life can be dark and threatening. However, as Dickinson tells us through the title of her poem, "we grow accustomed to the dark." This means that we will be able to find our way out of the darkness eventually.
It is interesting that the poet decided to use the first-person plural for her poem, as it is a lot more common for a poet to write in the first-person singular instead. In order to answer your question, you might want to point out that poets often use the first-person singular because they are writing about something personal and subjective, such as what they see, feel, or think. The use of the first-person singular in poetry therefore enforces that the message of the poem is a deeply personal message.
Using this as a starting point for your answer, you could then explain that the use of the first-person plural in this poem has a similar intention: the poet is still considering the message of her poem a very personal message. However, the poet also feels that her message affects all people and not just her. The feelings described in the poem connect us, as we are all experiencing similar feelings when we go through life.
Therefore, the poem allows the audience to feel a lot more connected with the poem, as it is not only a poem about the poet's feelings but a poem about feelings we all share. Therefore, the effect of the use of the first-person plural is that it makes the poem personal to everybody who reads it, not just to the poet.