What did Boromir want to do with the ring?

Boromir wanted the ring for himself because of the power it could afford him. In Book II, Chapter X, Boromir follows Frodo into the forest. Explaining his point-of-view, Boromir ultimately decides that Frodo ought to give up the Ring; of course, Frodo has grown more perceptive over time and he has long held Boromir in suspicion. When the man lunges at Frodo, to get the ring, Frodo slips the ring on - and disappears.