Final answer:
Iago plans to "help" Cassio by advising him to seek Desdemona's intercession with Othello, intending to use their meeting to fuel Othello's jealousy and further Iago's own vengeful plot.
Step-by-step explanation:
Iago's plan to "help" Cassio involves convincing him to appeal to Desdemona for help in restoring Othello's favor, which Cassio lost after being involved in a brawl that Iago orchestrated. Iago suggests that Desdemona's influence on her husband will ensure Cassio's reinstatement. However, Iago's real intent is to use Cassio's meeting with Desdemona to cast suspicion of infidelity between them in Othello's mind, as part of his larger scheme of manipulation and revenge.