So you are asking which two words in this poem show us that Homer is present in the poem? If so, I would say "deep-brow'd Homer" indicates that Homer is present. Other than that, there are many allusions to Homer and to the style in which Homer (if he existed) wrote.
For example, we see the presence of Homer when the poet speaks of "bards" who owe their allegiance to "Apollo." This is an allusion to Homer since he was a bard who was Greek and who would have possibly been loyal to Apollo. We see the phrase "western islands," which presumably refers to islands of the sort that Odysseus would have visited on his way home to Ithaka.
Keats uses the metaphors of demesne and discovery to indicate that he is experiencing the power of the ancient poet Homer. The unknown, in short, is becoming known. Readers may testify to the universality of Keats’s discovery by bringing out some of their own experiences with learning something for the first time. The metaphor of “travell’d” suggests that literature, like travel, takes us to new places, with all the acquisition of knowledge and experience that seeing new places implies. Keats uses the metaphors of “realms of gold,” “goodly states and kingdoms,” and “western islands,” to continue the power that Homer has transferred to Keats.