How we cite our quotes:
[…] I was prince of the apple towns
And once below a time I lordly had the trees and leaves (5-6)
So, the speaker doesn't come out and say, "I was young, once." But, he chooses to describe himself as "prince" and says, "once below a time." The figurative language here immediately sets the scene—he's young, he feels invincible, and he's got it made… for now.
Time let me play and be
Golden in the mercy of his means
And green and golden I was huntsman and herdsman, the calves
Sang to my horn, the foxes on the hills barked clear and cold (13-16)
Again, the speaker doesn't use the word youth, but by now we know he's describing what his youth felt like on the farm. It was a "golden" time and again, he seems to be in charge, as if youth has anointed him dominion over the landscape.
[…] it was air
And playing, lovely and watery
And fire green as grass. (20-22)
In stanza three, the speaker continues to praise youth. The "it" we think is youth, and the speaker leaves no doubt that he thought it was "lovely." Plus, the speaker's using nature imagery to describe youth, as if it were something as natural as the setting where he finds himself. This seems important because it expresses the speaker's belief that youth was something that shaped and was shaped by the landscape around him. Youth tied him to the setting and the speaker loved every inch of it.