How does Kipling give advice in terms of language, form, and structure?

Because your question asks for close reference to "the poem," I am going to assume you have miscategorized this question and are asking about Kipling's famous advisory poem, "If."
Kipling's poem, "If," a classic of Victorian stoicism, reflects the values of the society in which it was written. Kipling writes to an unidentified young man, whom he addresses directly: "my son." His choice to write in the second person, addressing the reader directly as "you," lends the poem an immediacy which helps each reader to imagine that it is personal to them; the choice of address fosters an intimacy between speaker and reader which suits the avuncular tone of the poem.
Kipling writes in iambic pentameter, lines with five "beats" or points of emphasis. This is the favored form of Shakespeare, a form extremely familiar to readers of English poetry and one which generally reflects the rhythms of speech. As such, this helps to convey the impression that the advice given in the poem is conversational, passed from one person to another. There is nothing contrived about the form; just as the language is generally straightforward and easy to understand so that the message is not obscured, the form is predictable and reliable, helping to create a sense of trust between speaker and reader, for the most part.
The structure of the poem, with its ABABCDCD rhyme scheme, lends it cohesion and a sense that the conclusion suggested by the repetitive pattern is inevitable if the rules are followed: as in Boolean algebra, if this, so this. The structure is an echo of the content. Only in the first stanza does Kipling deviate from this rhyme scheme: here, we see AAAABCBC. This has the effect of setting the first stanza apart almost as a preamble to what follows. It is particularly interesting to note the word that causes the rhyme scheme to diverge from the later ABABCDCD: the "you" which is repeated at the end of the first three lines. This directs the attention of the reader toward what the poem will privilege. The poem is about "you," the reader, and its focus is upon how to support "you" onward into the rhythmical and metrical stability which the rest of the poem displays.
The literary devices Kipling uses to convey his message in terms of language are effective in their simplicity. Parallelism and repetition emphasize the poem's point that "you" must simply follow the rules consistently in order to eventually "be a man, my son." Anaphora is a key device in the poem: "If you . . . if you . . . " and "Or . . . " are phrases which set up situations in which "you" may find yourself, and then follows the advice as to how one should conduct oneself.
The poem also uses the device of personification to give the impression that the challenges we may encounter in life are almost human, and can be fought as humans can. "Triumph and Disaster," the poet says, are "impostors," while "Will" alone is offered voice: "Hold on!" This suggests that Triumph and Disaster have, ultimately, less agency than the Will within us which will lend us our determination. Interesting, too, is the conversational tone into which the poet sometimes falls, with colloquialisms such as "build 'em up" and "talk too wise" (rather than "wisely") adding to the sense of almost conspiratorial intimacy established between author and reader. What the poet says, he says straightforwardly, which lends a depth of credence to his words. We feel he understands Triumph and Disaster through long experience, and has come to know what Will can achieve by the same means.
This poem is, in fact, one long, run-on sentence. Much of its efficacy lies in the fact that it is all leading, like a crescendo, to the final conclusion reached in the last sentence. The poet lays out every possible situation in which, "if" you behave in a particular way . . . but does not set out what the actual, physical consequence will be of any of this good behavior until the end of the poem. The poem's reliable structure and rhythm, combined with its personalized address, however, mean that the reader cannot be in any doubt that the consequence of if will be positive.